matplotlib-users Mailing List for matplotlib (Page 4)

On 2015/02/13 3:29 PM, Tommy Carstensen wrote:
> Is it possible to combine MultipleLocator and MaxNLocator? One seems
> to erase the effect of the other.

They are for different situations.  MultipleLocator is for when you know 
what you want your tick interval to be; MaxNLocator is for when you 
don't know that, but you do know roughly how many ticks you want, and 
what sort of numerical intervals are acceptable.

Eric

Is it possible to combine MultipleLocator and MaxNLocator? One seems
to erase the effect of the other.

How can I set the horizontal alignment of a secondary y-axis to
'right'? Currently the numbers are glued to the axis. I want the axis
values to be right aligned integers. Thanks.

On 2015-02-13 01:47, ralph hosmer wrote:
> download: matplotlib-1.4.2-cp32-none-win_amd64.whl  [from Sourceforge]
> my system: hp Pavilion 500-314 Desktop
>                      AMD A8-7600 Accelerated Processor
>                      Windows 8.1
> Python 3.4.2 (on Win32)
> PyCharm 4 Community Edition
>
> In the Python Command Line window, I've tried most of the "install
> matplotlib" instructions, but continue to get "Syntax Error".
> Double-clicking on the downloaded matplotlib (.whl) file asks what I
> want to use to open the file.
> I'm new to Python, and am a loss as to how to install "matplotlib"!
> Please Help !!

	Well, one thing is that an installer with "cp32" in the filename is for 
Python 3.2.  For Python 3.4 you need the one that says "cp34".

-- 
Brendan Barnwell
"Do not follow where the path may lead.  Go, instead, where there is no 
path, and leave a trail."
    --author unknown

On 12/02/2015 17:00, Paul Hobson wrote:
> Definitely. Assuming you don't want to do this in an interactive 
> manner (i.e. pointing and clicking with your mouse:
>
> fig, ax  = plt.subplots()
> ax.contour(...)
> ax.plot(x_dots, y_dots, 'ro', label='Dots')
> -p
>
> On Thu, Feb 12, 2015 at 8:07 AM, Dr Sydney Shall 
> <syd...@me... <mailto:syd...@me...>> wrote:
>
>     I am a beginner and I use Python 2.7 on an iMac OSX 10.9.5. Python is
>     the Enthought installation.
>     I am doing simulation experiments. I have constructed a 2D contour map
>     with my results and I am happy with the result.
>     I am wondering if it is possible to add the data points, say as red
>     dots, on this contour map.
>     I have not been able to find an equivalent example in gallery and I am
>     too much a novice to know what to do.
>     Any help would be much appreciated.
>
>     --
>     Sydney
>
Thanks Paul. Works perfectly.
I should have been able to work that out for myself, but my format was 
wrong.
Cheers.

-- 
Sydney

Hi Ralph,

On 2/13/2015 12:40, ralph hosmer wrote:
> Per your instructions, I downloaded [] and installed using the 
> 'wizard'.  The file I'm trying to execute is currently in a PyCharm 
> project, and the Error Trace I get is as follows:
>
> C:\Python34\python.exe 
> "C:/Users/Ralph/PycharmProjects/anuASTRO4x/src/Euler's Method.py"
> Traceback (most recent call last):
>   File "C:/Users/Ralph/PycharmProjects/anuASTRO4x/src/Euler's 
> Method.py", line 21, in <module>
>     import pylab # This program requires the matplotlib python library 
> for the plots.
>   File "C:\Python34\lib\site-packages\pylab.py", line 1, in <module>
>     from matplotlib.pylab import *
>   File "C:\Python34\lib\site-packages\matplotlib\__init__.py", line 
> 105, in <module>
>     import six
> ImportError: No module named 'six'
> Euler's Method
>
>
> 'from matplotlib.pylab import *' calls '__init__-py' and tries 
> [unsuccessfully] to 'import 'six'.
>
> What do you suggest I do to correct the ImportError: No module named 
> 'six' ?
Hhm, that is one of the requirements, see under the Windows section:
http://matplotlib.org/users/installing.html?highlight=requirements

You should be able to install them with 'pip' - e.g. 'pip install six'

numpy is a bit more of a hazzle, in the past Christoph Gohlke's site had 
.exe's but there are now wheels, so you need to download the correct one 
(win32 and py3.4) and then use pip to install it.

https://pip.pypa.io/en/latest/user_guide.html#installing-from-wheels
http://www.lfd.uci.edu/~gohlke/pythonlibs/

Werner

Per your instructions, I downloaded [] and installed using the 'wizard'.  The file I'm trying to execute is currently in a PyCharm project, and the Error Trace I get is as follows:
C:\Python34\python.exe "C:/Users/Ralph/PycharmProjects/anuASTRO4x/src/Euler's Method.py"Traceback (most recent call last):
  File "C:/Users/Ralph/PycharmProjects/anuASTRO4x/src/Euler's Method.py", line 21, in <module>
    import pylab # This program requires the matplotlib python library for the plots.
  File "C:\Python34\lib\site-packages\pylab.py", line 1, in <module>
    from matplotlib.pylab import *
  File "C:\Python34\lib\site-packages\matplotlib\__init__.py", line 105, in <module>
    import six
ImportError: No module named 'six'
Euler's Method

'from matplotlib.pylab import *' calls '__init__-py' and tries [unsuccessfully] to 'import 'six'.
What do you suggest I do to correct the ImportError: No module named 'six' ?Thanks for the help, Ralph

On 13 February 2015 at 11:47, ralph hosmer <ral...@ya...> wrote:
> download: matplotlib-1.4.2-cp32-none-win_amd64.whl  [from Sourceforge]
>
> In the Python Command Line window, I've tried most of the "install
> matplotlib" instructions, but continue to get "Syntax Error".
> Double-clicking on the downloaded matplotlib (.whl) file asks what I want to
> use to open the file.
> I'm new to Python, and am a loss as to how to install "matplotlib"! Please
> Help !!

You'll probably have an easier time if you install one of the
"batteries included" Python distributions listed here -
http://www.scipy.org/install.html

Then you can get started without needing to learn how and where Python
packages are installed.

Cheers,
Scott

download: matplotlib-1.4.2-cp32-none-win_amd64.whl  [from Sourceforge]my system: hp Pavilion 500-314 Desktop                    AMD A8-7600 Accelerated Processor                    Windows 8.1Python 3.4.2 (on Win32)PyCharm 4 Community Edition
In the Python Command Line window, I've tried most of the "install matplotlib" instructions, but continue to get "Syntax Error".Double-clicking on the downloaded matplotlib (.whl) file asks what I want to use to open the file.I'm new to Python, and am a loss as to how to install "matplotlib"! Please Help !!

On Mon, Feb 9, 2015 at 1:00 AM, Thomas Caswell <tca...@gm...> wrote:
> Sorry about the bad tarball, I forgot to clean my git directory before
> generating it.  Another point in favor of using the gh tarball, I can't
> screw it up.

I switch to GH tarball, but I must say they are a lot different than
the SF ones (now we have 3 copies of the examples in doc/mpl_examples
lib/mpl_examples and examples) and contains quite a lot more files
(like the whole unit/ tree) and development files (.travis, .gitignore
and friends), but if that's a more reliable way to get new tarball,
I'm all for it - let's use this in the future :)

> This is the first I have seen that CVE.
>
> That PR is not included in 1.4.3 because it completely over-hauls how the
> Agg rendering works (and generated a whole bunch of other bugs along the
> way).
>
> Mike: Is there a way to fix up the security issues reported on just the
> 1.4.x branch with out pulling that whole patch back?

there is a patch[1] attached to the Debian bug[2], I'm about to apply
to the package and see how it goes, you might want to
investigate+apply it in the final release

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?msg=5;filename=matplotlib-printf-buffer-overrun.patch;att=1;bug=775691
[2] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=775691

Cheers,
-- 
Sandro Tosi (aka morph, morpheus, matrixhasu)
My website: http://matrixhasu.altervista.org/
Me at Debian: http://wiki.debian.org/SandroTosi

Ryan,
Thanks again. I have the permissions, I'll reinstall.

John

On 2/12/2015 11:43 AM, Ryan Nelson wrote:
> John,
>
> It's been a little while since I installed QGIS on my machine, but I 
> wonder if you missed a selection somewhere in the installation 
> process. Can you reinstall QGIS? (i.e. do you have admin permissions?) 
> There might be a number of selections you can make when installing, 
> and my guess is that you missed a selection to have the proper Python 
> libraries installed. Maybe there is a "Full" installation option, 
> which puts everything on your machine. As I said on my installation of 
> QGIS, that code works just fine, and I'm certain that I haven't done 
> anything special post-install.
>
> Ryan
>
> On Thu, Feb 12, 2015 at 12:37 PM, john polo <jp...@ma... 
> <mailto:jp...@ma...>> wrote:
>
>     Ryan,
>     I used the first line of your example and this was the result:
>     Traceback (most recent call last):
>       File "<input>", line 1, in <module>
>       File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 454,
>     in _import
>         mod = _builtin_import(name, globals, locals, fromlist, level)
>     ImportError: No module named matplotlib.pyplot
>
>     I'm not sure what the first command is to confirm whether a module
>     is installed or not, but it looks like I may need that.
>     Thanks, Ben and Ryan.
>
>     John
>
>
>     On 2/12/2015 10:09 AM, Ryan Nelson wrote:
>>     John,
>>
>>     As Ben said, the QGIS Windows installer comes with its own Python
>>     installation, which doesn't know anything about any other Python
>>     install. Unfortunately, this apparently makes it rather difficult
>>     to install other packages. However, QGIS Python already contains
>>     Numpy and Matplotlib and PyQt4, which is what you need here. From
>>     the Plugins dropdown menu, select Python Console. In the console
>>     that opens at the bottom of the screen, you should be able to
>>     type (don't type the > characters):
>>     >>> import matplotlib.pyplot as plt
>>     >>> plt.plot([1,2,3])
>>     >>> plt.show()
>>
>>     On my install of QGIS, that opens a pop-up window with a plot of
>>     those data points. Does this throw an error for you too?
>>
>>     Ryan
>>
>>     On Thu, Feb 12, 2015 at 10:35 AM, john polo <jp...@ma...
>>     <mailto:jp...@ma...>> wrote:
>>
>>         Users,
>>         I am working on Windows 7 with QGIS 2.4. I am trying to get a
>>         plugin
>>         installed in QGIS called Semi-Automatic Classification Plugin
>>         to work.
>>         The plugin is demonstrated here:
>>         http://fromgistors.blogspot.com/2013/07/working-with-multispectral-bands-in-qgis.html
>>
>>         The first time I tried to install the QGIS plugin, I got an error
>>         message that backend_qt4agg was not installed. I installed
>>         Python(x,y)
>>         with Python 2.x, because it seemed like the easiest way to get
>>         matplotlib and a bunch of other apps/extensions installed at
>>         the same
>>         time with minimal effort. I am not a programmer and I'm not
>>         familiar
>>         with installing things from source and then configuring
>>         settings. After
>>         the Python(x,y) install, I went to QGIS and started again and
>>         tried to
>>         install the plugin. I got the same error message. Please tell
>>         me what I
>>         need to do to get this backend installed in order to get the
>>         QGIS plugin
>>         I want.
>>
>>         John Polo
>>
>>
>>         ------------------------------------------------------------------------------
>>         Dive into the World of Parallel Programming. The Go Parallel
>>         Website,
>>         sponsored by Intel and developed in partnership with Slashdot
>>         Media, is your
>>         hub for all things parallel software development, from weekly
>>         thought
>>         leadership blogs to news, videos, case studies, tutorials and
>>         more. Take a
>>         look and join the conversation now.
>>         http://goparallel.sourceforge.net/
>>         _______________________________________________
>>         Matplotlib-users mailing list
>>         Mat...@li...
>>         <mailto:Mat...@li...>
>>         https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>>
>>
>
>

John,

It's been a little while since I installed QGIS on my machine, but I wonder
if you missed a selection somewhere in the installation process. Can you
reinstall QGIS? (i.e. do you have admin permissions?) There might be a
number of selections you can make when installing, and my guess is that you
missed a selection to have the proper Python libraries installed. Maybe
there is a "Full" installation option, which puts everything on your
machine. As I said on my installation of QGIS, that code works just fine,
and I'm certain that I haven't done anything special post-install.

Ryan

On Thu, Feb 12, 2015 at 12:37 PM, john polo <jp...@ma...> wrote:

>  Ryan,
> I used the first line of your example and this was the result:
> Traceback (most recent call last):
>   File "<input>", line 1, in <module>
>   File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 454, in _import
>     mod = _builtin_import(name, globals, locals, fromlist, level)
> ImportError: No module named matplotlib.pyplot
>
> I'm not sure what the first command is to confirm whether a module is
> installed or not, but it looks like I may need that.
> Thanks, Ben and Ryan.
>
> John
>
>
> On 2/12/2015 10:09 AM, Ryan Nelson wrote:
>
> John,
>
>  As Ben said, the QGIS Windows installer comes with its own Python
> installation, which doesn't know anything about any other Python install.
> Unfortunately, this apparently makes it rather difficult to install other
> packages. However, QGIS Python already contains Numpy and Matplotlib and
> PyQt4, which is what you need here. From the Plugins dropdown menu, select
> Python Console. In the console that opens at the bottom of the screen, you
> should be able to type (don't type the > characters):
> >>> import matplotlib.pyplot as plt
> >>> plt.plot([1,2,3])
> >>> plt.show()
>
>  On my install of QGIS, that opens a pop-up window with a plot of those
> data points. Does this throw an error for you too?
>
>  Ryan
>
> On Thu, Feb 12, 2015 at 10:35 AM, john polo <jp...@ma...> wrote:
>
>> Users,
>> I am working on Windows 7 with QGIS 2.4. I am trying to get a plugin
>> installed in QGIS called Semi-Automatic Classification Plugin to work.
>> The plugin is demonstrated here:
>>
>> http://fromgistors.blogspot.com/2013/07/working-with-multispectral-bands-in-qgis.html
>>
>> The first time I tried to install the QGIS plugin, I got an error
>> message that backend_qt4agg was not installed. I installed Python(x,y)
>> with Python 2.x, because it seemed like the easiest way to get
>> matplotlib and a bunch of other apps/extensions installed at the same
>> time with minimal effort. I am not a programmer and I'm not familiar
>> with installing things from source and then configuring settings. After
>> the Python(x,y) install, I went to QGIS and started again and tried to
>> install the plugin. I got the same error message. Please tell me what I
>> need to do to get this backend installed in order to get the QGIS plugin
>> I want.
>>
>> John Polo
>>
>>
>>
>> ------------------------------------------------------------------------------
>> Dive into the World of Parallel Programming. The Go Parallel Website,
>> sponsored by Intel and developed in partnership with Slashdot Media, is
>> your
>> hub for all things parallel software development, from weekly thought
>> leadership blogs to news, videos, case studies, tutorials and more. Take a
>> look and join the conversation now. http://goparallel.sourceforge.net/
>> _______________________________________________
>> Matplotlib-users mailing list
>> Mat...@li...
>> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>>
>
>
>

Ryan,
I used the first line of your example and this was the result:
Traceback (most recent call last):
   File "<input>", line 1, in <module>
   File "C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 454, in _import
     mod = _builtin_import(name, globals, locals, fromlist, level)
ImportError: No module named matplotlib.pyplot

I'm not sure what the first command is to confirm whether a module is 
installed or not, but it looks like I may need that.
Thanks, Ben and Ryan.

John

On 2/12/2015 10:09 AM, Ryan Nelson wrote:
> John,
>
> As Ben said, the QGIS Windows installer comes with its own Python 
> installation, which doesn't know anything about any other Python 
> install. Unfortunately, this apparently makes it rather difficult to 
> install other packages. However, QGIS Python already contains Numpy 
> and Matplotlib and PyQt4, which is what you need here. From the 
> Plugins dropdown menu, select Python Console. In the console that 
> opens at the bottom of the screen, you should be able to type (don't 
> type the > characters):
> >>> import matplotlib.pyplot as plt
> >>> plt.plot([1,2,3])
> >>> plt.show()
>
> On my install of QGIS, that opens a pop-up window with a plot of those 
> data points. Does this throw an error for you too?
>
> Ryan
>
> On Thu, Feb 12, 2015 at 10:35 AM, john polo <jp...@ma... 
> <mailto:jp...@ma...>> wrote:
>
>     Users,
>     I am working on Windows 7 with QGIS 2.4. I am trying to get a plugin
>     installed in QGIS called Semi-Automatic Classification Plugin to work.
>     The plugin is demonstrated here:
>     http://fromgistors.blogspot.com/2013/07/working-with-multispectral-bands-in-qgis.html
>
>     The first time I tried to install the QGIS plugin, I got an error
>     message that backend_qt4agg was not installed. I installed Python(x,y)
>     with Python 2.x, because it seemed like the easiest way to get
>     matplotlib and a bunch of other apps/extensions installed at the same
>     time with minimal effort. I am not a programmer and I'm not familiar
>     with installing things from source and then configuring settings.
>     After
>     the Python(x,y) install, I went to QGIS and started again and tried to
>     install the plugin. I got the same error message. Please tell me
>     what I
>     need to do to get this backend installed in order to get the QGIS
>     plugin
>     I want.
>
>     John Polo
>
>
>     ------------------------------------------------------------------------------
>     Dive into the World of Parallel Programming. The Go Parallel Website,
>     sponsored by Intel and developed in partnership with Slashdot
>     Media, is your
>     hub for all things parallel software development, from weekly thought
>     leadership blogs to news, videos, case studies, tutorials and
>     more. Take a
>     look and join the conversation now. http://goparallel.sourceforge.net/
>     _______________________________________________
>     Matplotlib-users mailing list
>     Mat...@li...
>     <mailto:Mat...@li...>
>     https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>
>

Definitely. Assuming you don't want to do this in an interactive manner
(i.e. pointing and clicking with your mouse:

fig, ax  = plt.subplots()
ax.contour(...)
ax.plot(x_dots, y_dots, 'ro', label='Dots')
-p

On Thu, Feb 12, 2015 at 8:07 AM, Dr Sydney Shall <syd...@me...>
wrote:

> I am a beginner and I use Python 2.7 on an iMac OSX 10.9.5. Python is
> the Enthought installation.
> I am doing simulation experiments. I have constructed a 2D contour map
> with my results and I am happy with the result.
> I am wondering if it is possible to add the data points, say as red
> dots, on this contour map.
> I have not been able to find an equivalent example in gallery and I am
> too much a novice to know what to do.
> Any help would be much appreciated.
>
> --
> Sydney
>
>
>
> ------------------------------------------------------------------------------
> Dive into the World of Parallel Programming. The Go Parallel Website,
> sponsored by Intel and developed in partnership with Slashdot Media, is
> your
> hub for all things parallel software development, from weekly thought
> leadership blogs to news, videos, case studies, tutorials and more. Take a
> look and join the conversation now. http://goparallel.sourceforge.net/
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>

I am a beginner and I use Python 2.7 on an iMac OSX 10.9.5. Python is 
the Enthought installation.
I am doing simulation experiments. I have constructed a 2D contour map 
with my results and I am happy with the result.
I am wondering if it is possible to add the data points, say as red 
dots, on this contour map.
I have not been able to find an equivalent example in gallery and I am 
too much a novice to know what to do.
Any help would be much appreciated.

-- 
Sydney

John,

As Ben said, the QGIS Windows installer comes with its own Python
installation, which doesn't know anything about any other Python install.
Unfortunately, this apparently makes it rather difficult to install other
packages. However, QGIS Python already contains Numpy and Matplotlib and
PyQt4, which is what you need here. From the Plugins dropdown menu, select
Python Console. In the console that opens at the bottom of the screen, you
should be able to type (don't type the > characters):
>>> import matplotlib.pyplot as plt
>>> plt.plot([1,2,3])
>>> plt.show()

On my install of QGIS, that opens a pop-up window with a plot of those data
points. Does this throw an error for you too?

Ryan

On Thu, Feb 12, 2015 at 10:35 AM, john polo <jp...@ma...> wrote:

> Users,
> I am working on Windows 7 with QGIS 2.4. I am trying to get a plugin
> installed in QGIS called Semi-Automatic Classification Plugin to work.
> The plugin is demonstrated here:
>
> http://fromgistors.blogspot.com/2013/07/working-with-multispectral-bands-in-qgis.html
>
> The first time I tried to install the QGIS plugin, I got an error
> message that backend_qt4agg was not installed. I installed Python(x,y)
> with Python 2.x, because it seemed like the easiest way to get
> matplotlib and a bunch of other apps/extensions installed at the same
> time with minimal effort. I am not a programmer and I'm not familiar
> with installing things from source and then configuring settings. After
> the Python(x,y) install, I went to QGIS and started again and tried to
> install the plugin. I got the same error message. Please tell me what I
> need to do to get this backend installed in order to get the QGIS plugin
> I want.
>
> John Polo
>
>
>
> ------------------------------------------------------------------------------
> Dive into the World of Parallel Programming. The Go Parallel Website,
> sponsored by Intel and developed in partnership with Slashdot Media, is
> your
> hub for all things parallel software development, from weekly thought
> leadership blogs to news, videos, case studies, tutorials and more. Take a
> look and join the conversation now. http://goparallel.sourceforge.net/
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>

I doubt that installing Python(x,y) would help because it is a
self-contained distribution of python. QGIS wouldn't necessarally know
about the libraries that it provides. Your best bet is to ask this question
to the QGIS people who better understands how their software is installed
in the Windows environment. How QGIS is installed is critical to
understanding what libraries it can and can not access.

Of course, you could also try one of the windows binary installers of
matplotlib, but I don't know if they come with the Qt4 environment or not.

Cheers!
Ben Root


On Thu, Feb 12, 2015 at 10:35 AM, john polo <jp...@ma...> wrote:

> Users,
> I am working on Windows 7 with QGIS 2.4. I am trying to get a plugin
> installed in QGIS called Semi-Automatic Classification Plugin to work.
> The plugin is demonstrated here:
>
> http://fromgistors.blogspot.com/2013/07/working-with-multispectral-bands-in-qgis.html
>
> The first time I tried to install the QGIS plugin, I got an error
> message that backend_qt4agg was not installed. I installed Python(x,y)
> with Python 2.x, because it seemed like the easiest way to get
> matplotlib and a bunch of other apps/extensions installed at the same
> time with minimal effort. I am not a programmer and I'm not familiar
> with installing things from source and then configuring settings. After
> the Python(x,y) install, I went to QGIS and started again and tried to
> install the plugin. I got the same error message. Please tell me what I
> need to do to get this backend installed in order to get the QGIS plugin
> I want.
>
> John Polo
>
>
>
> ------------------------------------------------------------------------------
> Dive into the World of Parallel Programming. The Go Parallel Website,
> sponsored by Intel and developed in partnership with Slashdot Media, is
> your
> hub for all things parallel software development, from weekly thought
> leadership blogs to news, videos, case studies, tutorials and more. Take a
> look and join the conversation now. http://goparallel.sourceforge.net/
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>

Users,
I am working on Windows 7 with QGIS 2.4. I am trying to get a plugin 
installed in QGIS called Semi-Automatic Classification Plugin to work. 
The plugin is demonstrated here:
http://fromgistors.blogspot.com/2013/07/working-with-multispectral-bands-in-qgis.html

The first time I tried to install the QGIS plugin, I got an error 
message that backend_qt4agg was not installed. I installed Python(x,y) 
with Python 2.x, because it seemed like the easiest way to get 
matplotlib and a bunch of other apps/extensions installed at the same 
time with minimal effort. I am not a programmer and I'm not familiar 
with installing things from source and then configuring settings. After 
the Python(x,y) install, I went to QGIS and started again and tried to 
install the plugin. I got the same error message. Please tell me what I 
need to do to get this backend installed in order to get the QGIS plugin 
I want.

John Polo

Thanks Paul, your explanation makes perfectly sense.

Indeed, computing "manually" the PDS (using numpy.fft) in a test case gives
me equal power for sine wave component of same amplitude, even when a
component is in the highest frequency bin.

However, giving the same test case to matplotlib.mlab.specgram() results in
the power density of the highest frequency bin being higher than the other
components.

For the test see this notebook:
http://nbviewer.ipython.org/gist/tritemio/162925a69a6ec29cdfe1


Antonio


On Wed, Feb 11, 2015 at 8:50 PM, Paul Blelloch <pau...@at...>
wrote:

> I’m just answering off the top of my head, but it would seem to make sense
> to me that neither the 0 frequency nor the fmax frequency should be scaled
> by 2.  If you take an FFT of a signal of length N, you’ll get a transform
> of length N.  N/2 points will correspond to positive frequencies, one point
> to zero frequency and N/2-1 points to negative frequency.  So it’s the
> N/2-1 points that are reflected to the positive frequency axis, and the
> fmax frequency is the only one that doesn’t have a corresponding point on
> the negative axis.
>
>
>
> On the practical side, I’d say that you’re asking for trouble if you’re
> looking at the last frequency bin in a power spectrum.  If there’s any
> significant energy in that bin, there’s almost certainly energy at higher
> frequencies that’s being aliased down.  You really need to make sure that
> you have negligible power content before you get to the Nyquist frequency,
> usually by applying an analog filter to the data, or otherwise knowing that
> it cannot have undesired high frequency content.
>
>
>
> *From:* Antonino Ingargiola [mailto:tri...@gm...]
> *Sent:* Wednesday, February 11, 2015 6:45 PM
> *To:* mat...@li...
> *Subject:* [Matplotlib-users] mlab: computing power spectra
>
>
>
> Hi to all,
>
>
>
> I'm computing some spectrograms using the convenient functions defined in
> matplotlib.mlab.
>
>
>
> I found something that I don't completely understand. In computing the PSD
> the onesided power spectrum is scaled by a factor of 2 except for the first
> and the last bin:
>
>
>
>
> https://github.com/matplotlib/matplotlib/blob/v1.4.2/lib/matplotlib/mlab.py#L776
>
>
>
> in principle this should account for the contributions that in a two-sided
> spectrum is spread over negative and positive frequencies. However the lack
> of scaling in the highest frequency seems to cause a systematic
> underestimation on that frequency bin.
>
>
>
> Is it possible that the power spectrum should  be scaled, in the case of
> even-length signal, up to the last bin (so that -1 in the slicing should be
> removed)?
>
>
>
> With correct scaling a signal comprised of two sinusoids of same power,
> one being at the Nyquist frequency, should have the same amplitude
> (excluding scallopping losses). I don't have time to test it at the moment,
> but maybe someone more expert can already tell me if I'm missing something
> or the matplotlib scaling is wrong.
>
>
>
> Thanks,
>
> Antonio
>

Hi to all,

I'm computing some spectrograms using the convenient functions defined in
matplotlib.mlab.

I found something that I don't completely understand. In computing the PSD
the onesided power spectrum is scaled by a factor of 2 except for the first
and the last bin:

https://github.com/matplotlib/matplotlib/blob/v1.4.2/lib/matplotlib/mlab.py#L776

in principle this should account for the contributions that in a two-sided
spectrum is spread over negative and positive frequencies. However the lack
of scaling in the highest frequency seems to cause a systematic
underestimation on that frequency bin.

Is it possible that the power spectrum should  be scaled, in the case of
even-length signal, up to the last bin (so that -1 in the slicing should be
removed)?

With correct scaling a signal comprised of two sinusoids of same power, one
being at the Nyquist frequency, should have the same amplitude (excluding
scallopping losses). I don't have time to test it at the moment, but maybe
someone more expert can already tell me if I'm missing something or the
matplotlib scaling is wrong.

Thanks,
Antonio

Sorry this didn't get a response for so long.

The core of the embedding in Qt is at QWidget which contains the canvas.
Anything you want to do with a QWidget you can do with the canvas.
Independently
you need to maintain the mpl level plotting objects (the Figure, Axes, and
Artist objects) (well, you don't _need_ to, you can get to them through the
canvas object, but to keep your self sane I highly recommend keeping track
of the mpl objects your self, this linkage is there so that GUI generated
draw commands can trigger a re-rendering of the figure).

I would just have a widget for each of the plots you want to have and then
cycle which one is visible in the main window, that is probably a lot
easier than trying to attach and detach canvases from Figures.

I would also take a look at glue
http://www.glueviz.org/en/stable/installation.html who may have solved many
of these problems for you.

Tom

On Thu Feb 05 2015 at 1:03:16 PM tenspd137 . <dcd...@gm...> wrote:

> Hi all,
>
> I often have scripts that make a lot of plots, and I would like to be
> able to create the plots and then have a UI tool that shows a list of
> their titles, click on the title and have the plot be drawn in a
> window.  So far, I have been able to use PyQt to create a UI with a
> list box and a Widget to display plots.  What I can't seem to figure
> out is how to make a bunch of plots and then have the Window update.
>
> So, in psuedo code:
>
> list of plots = []
>
> Go through datasets:
>         plots.append(plot(dataset))
>
> For plot in plots:
>        add plot title to UI list, position in list is reference back
> into list of plots
>
> On UI:
>         click on plot name/title
>         widget draws plot
>
>
> So - basically like docked plots, except there is just a list to the
> side instead (much cleaner IMHO)
>
> I haven't been able to find any examples from googling.  Has any one
> been able to do this or seen examples?
>
>
> Any help or suggestions are appreciated!
>
> Thanks!
>
> :
>
> ------------------------------------------------------------
> ------------------
> Dive into the World of Parallel Programming. The Go Parallel Website,
> sponsored by Intel and developed in partnership with Slashdot Media, is
> your
> hub for all things parallel software development, from weekly thought
> leadership blogs to news, videos, case studies, tutorials and more. Take a
> look and join the conversation now. http://goparallel.sourceforge.net/
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>

Dear matplotlib users,

The INCF (incf.org) is sponsoring two Google Summer of Code projects
this year that will directly benefit PyDSTool (pydstool.sf.net), a
math modeling toolbox for science and engineering that some of you
will know. One, if not both, of the projects will involve significant
technical usage of MPL's 2D GUI widgets as well as building new types
of model visualization tools over MPL. MPL has been chosen to maximize
platform independence and minimize reliance on additional user
installation of third party libraries, and is well suited for the
prototyping of application front ends for research code.

Please forward to anyone who might be interested in participating:

http://incf.org/gsoc/2015/proposals/#-span--span----nbsp---span---span--span-neuroscience-model-exploration-and-development-tools-for-pydstool--span-

http://www.google-melange.com/gsoc/homepage/google/gsoc2015

Thanks,
Rob

On 2015/02/09 8:19 AM, Thomas Caswell wrote:
> Can you test with 1.4.3rc1?  I believe this has been fixed.

Oops!  Of course--I never use ',', and I was forgetting that it *is* 
just one pixel.

Eric

>
> On Mon Feb 09 2015 at 1:07:28 PM Alex Böhnert <ale...@gm...
> <mailto:ale...@gm...>> wrote:
>
>     Dear all,
>
>     when plotting scattered data with the "," marker, the data points do
>     not show up either on screen (Qt4Agg backend) or in saved bitmap
>     images (tested with png); they do show up if the plot is exported as
>     pdf.
>
>     Example code (run in "ipython --pylab" for simplicity):
>
>     import numpy as np
>     a = np.random.standard_normal(500)
>     b = np.random.standard_normal(500)
>     plot(a,b,',')
>     savefig("testplot.png")
>     savefig("testplot.pdf")
>
>     Expected result: Scatter plot of random data points, both on screen
>     and in saved files.
>
>     Actual result: Empty-looking plot both on screen and in png, but
>     plot as expected in pdf.
>
>     System info: Arch linux, Kernel 3.17.6 (and 3.18.6), matplotlib
>     version 1.4.2, Python 3.4.2, IPython 2.3.1., numpy version 1.9.1,
>     Qt4Agg backend.
>
>     Related: I posted this to the arch-bugtracker
>     (https://bugs.archlinux.org/task/43392) and asked on stack overflow
>     whether anyone else saw this
>     (http://stackoverflow.com/questions/28112916/python-matplotlib-does-not-display-data-points-bug-or-something-else).
>     Apparently, the same thing happens in Ubuntu, too.
>
>     Hope this is the right place to report this.
>
>     Cheers,
>     Alex
>
>     P.S.: I sent the same mail to the list a few weeks ago without
>     registering, but it was never posted, nor replied to. It might be a
>     good idea not to suggest at
>     http://matplotlib.org/faq/troubleshooting_faq.html#getting-help that
>     just sending a mail to the list will achieve anything...
>     ------------------------------__------------------------------__------------------
>     Dive into the World of Parallel Programming. The Go Parallel Website,
>     sponsored by Intel and developed in partnership with Slashdot Media,
>     is your
>     hub for all things parallel software development, from weekly thought
>     leadership blogs to news, videos, case studies, tutorials and more.
>     Take a
>     look and join the conversation now.
>     http://goparallel.sourceforge.__net/
>     <http://goparallel.sourceforge.net/>_________________________________________________
>     Matplotlib-users mailing list
>     Matplotlib-users@lists.__sourceforge.net
>     <mailto:Mat...@li...>
>     https://lists.sourceforge.net/__lists/listinfo/matplotlib-__users
>     <https://lists.sourceforge.net/lists/listinfo/matplotlib-users>
>
>
>
> ------------------------------------------------------------------------------
> Dive into the World of Parallel Programming. The Go Parallel Website,
> sponsored by Intel and developed in partnership with Slashdot Media, is your
> hub for all things parallel software development, from weekly thought
> leadership blogs to news, videos, case studies, tutorials and more. Take a
> look and join the conversation now. http://goparallel.sourceforge.net/
>
>
>
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>

Thomas Caswell wrote
> Can you test with 1.4.3rc1?  I believe this has been fixed.

I just built 1.4.3-rc1 (from the Download page->other Downloads ->
Older/mics) from source. It seems to indeed be fixed there.

Thanks a lot!




--
View this message in context: http://matplotlib.1069221.n5.nabble.com/Bug-in-matplotlib-1-4-2-tp44850p44853.html
Sent from the matplotlib - users mailing list archive at Nabble.com.

On 2015/02/09 8:19 AM, Thomas Caswell wrote:
> Can you test with 1.4.3rc1?  I believe this has been fixed.

I don't think so.  I can reproduce it on master.  Regardless of the "ms" 
kwarg, I see only a pixel.

Eric

>
> On Mon Feb 09 2015 at 1:07:28 PM Alex Böhnert <ale...@gm...
> <mailto:ale...@gm...>> wrote:
>
>     Dear all,
>
>     when plotting scattered data with the "," marker, the data points do
>     not show up either on screen (Qt4Agg backend) or in saved bitmap
>     images (tested with png); they do show up if the plot is exported as
>     pdf.
>
>     Example code (run in "ipython --pylab" for simplicity):
>
>     import numpy as np
>     a = np.random.standard_normal(500)
>     b = np.random.standard_normal(500)
>     plot(a,b,',')
>     savefig("testplot.png")
>     savefig("testplot.pdf")
>
>     Expected result: Scatter plot of random data points, both on screen
>     and in saved files.
>
>     Actual result: Empty-looking plot both on screen and in png, but
>     plot as expected in pdf.
>
>     System info: Arch linux, Kernel 3.17.6 (and 3.18.6), matplotlib
>     version 1.4.2, Python 3.4.2, IPython 2.3.1., numpy version 1.9.1,
>     Qt4Agg backend.
>
>     Related: I posted this to the arch-bugtracker
>     (https://bugs.archlinux.org/task/43392) and asked on stack overflow
>     whether anyone else saw this
>     (http://stackoverflow.com/questions/28112916/python-matplotlib-does-not-display-data-points-bug-or-something-else).
>     Apparently, the same thing happens in Ubuntu, too.
>
>     Hope this is the right place to report this.
>
>     Cheers,
>     Alex
>
>     P.S.: I sent the same mail to the list a few weeks ago without
>     registering, but it was never posted, nor replied to. It might be a
>     good idea not to suggest at
>     http://matplotlib.org/faq/troubleshooting_faq.html#getting-help that
>     just sending a mail to the list will achieve anything...
>     ------------------------------__------------------------------__------------------
>     Dive into the World of Parallel Programming. The Go Parallel Website,
>     sponsored by Intel and developed in partnership with Slashdot Media,
>     is your
>     hub for all things parallel software development, from weekly thought
>     leadership blogs to news, videos, case studies, tutorials and more.
>     Take a
>     look and join the conversation now.
>     http://goparallel.sourceforge.__net/
>     <http://goparallel.sourceforge.net/>_________________________________________________
>     Matplotlib-users mailing list
>     Matplotlib-users@lists.__sourceforge.net
>     <mailto:Mat...@li...>
>     https://lists.sourceforge.net/__lists/listinfo/matplotlib-__users
>     <https://lists.sourceforge.net/lists/listinfo/matplotlib-users>
>
>
>
> ------------------------------------------------------------------------------
> Dive into the World of Parallel Programming. The Go Parallel Website,
> sponsored by Intel and developed in partnership with Slashdot Media, is your
> hub for all things parallel software development, from weekly thought
> leadership blogs to news, videos, case studies, tutorials and more. Take a
> look and join the conversation now. http://goparallel.sourceforge.net/
>
>
>
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>