matplotlib-users Mailing List for matplotlib (Page 5)

Hi:

I encounter the following problems, most are related to log plots.  I am using
version 0.54.1 on Solaris.  Did I miss something trivial?


(1) No y tick labels when the range is less than 10, e.g.
>>> semilogy([8,5,6,4,5,6,7])

(2) The 0.3 tick mark is missing in this plot:
>>> semilogy([56,7,2,0.2,999])

(3) If we do the "linear" plot first and then overplot it with the (semi)log 
plot, the lowest Y label (1) is totally wrong and the lowest order of magnitude 
has no tick marks! e.g.
>>> plot([8,5,6,4,5,6,7])
>>> semilogy([56,7,2,0.2,999])

(4) When doing semilogx(), it is always necessary to issue the show() command 
afterwards, to see the plot.  Not so for plot() or semilogy().

JC Hsu

>>>>> "Flavio" == Flavio Codeco Coelho <fcc...@fi...> writes:

    Flavio> John, I think it would be a good Idea to beef up the two
    Flavio> scales example by adding a second plot were the y axes
    Flavio> were independent while the x axis is shared. This is a
    Flavio> more common use of two scales.

Now you've confused me.  In two_scales.py, the x axis *is shared* and
there are two independent y axes.  I agree that this is the common use
case for multiple scales on the same axes, but that is what two_scales
already does.

Do you mean something like examples/ganged_plots.py by chance?

JDH

>>>>> "Flavio" == Flavio Codeco Coelho <fcc...@fi...> writes:

    Flavio> Crystal! But then the legends second example(legend_demo2)
    Flavio> is a bit misleading since it uses the syntax I used
    Flavio> originally (without the subscripts). I am aware of the
    Flavio> difference between the two situations, but my general
    Flavio> point is that since the examples are one of the main
    Flavio> sources of instruction for users, they should be as
    Flavio> complete as possible, i.e. contain as many variations on
    Flavio> the theme as possible, don't you agree?  Of course they
    Flavio> should not substitute the prime directive: RTFM!, but they
    Flavio> are a powerful tool that should be explored.

Well, in this case it would be RTNYEFM (RT not-yet-existant FM) so I
would hesitate to advise it.  Yes, the difference in your example and
the one in legend_demo2.py is that in the latter the sequence of lines
returned by plot are length 1 whereas in hist they are longer.  The
legend code "flattens" the list of lines/patches and so consumes the
sequences in order until the list of labels is exhausted.  In your
original example, the patches from the first hist used up all your
labels.

I changed legend_demo2.py to read

l1, = plot(t2, exp(-t2))
l2, l3 = plot(t2, sin(2*pi*t2), '--go', t1, log(1+t1), '.')
l4, = plot(t2, exp(-t2)*sin(2*pi*t2), 'rs-.')


legend( (l2, l4), ('oscillatory', 'damped'), 'upper right')

Adding the commas after l1 and l4 unpack the sequence returned by
plot, so l1 and l4 are now Line2D instances, not a sequence of lines.

This whole business of return values being objects or sequences of
objects is obscured by the fact that 'set' will operate on either,
which is true for matlab, BTW.

JDH

>>>>> "Flavio" == Flavio Codeco Coelho <fcc...@fi...> writes:

    Flavio> Hi, Is there a way to set the color of an histogram? what
    Flavio> about transparency ?

    Flavio> for example:

    Flavio> h=hist(x...  set(h,'alpha',0.75)

Of course, not all backends support the alpha channel (eg postscript),
but this is already possible with the agg backend

Here is some example code

    n, binsb, pb = hist(sb, 100,normed=True)
    set(pb, 'facecolor', 'r', 'alpha', 1.0)

Perhaps the problem with your test code above is that histogram
returns a tuple of (counts, bins, patches) and you need to set the
alpha on the patches only.

    Flavio> I would like to superimpose histograms on the same plot
    Flavio> but they would have to be of different colors and be
    Flavio> translucent.

    Flavio> I need to do this in using the matlab interface, not the
    Flavio> API.

Yep, I've done exactly this before using the code above; here's an
example image where one histogram is translucent gray superimposed
over a red histogram

http://nitace.bsd.uchicago.edu:8080/files/share/aptopower.png

JDH

>>>>> "Peter" == Peter Groszkowski <pgr...@ge...> writes:

    Peter> seems like axes.plot_date() does not return the lines it
    Peter> creates... by looking at matlab.plot_date(), and comparing
    Peter> those with the case for regular plot() I think it
    Peter> should.. so we have a missing return statement..

Duly noted, fixed.  Thanks.

JDH

seems like axes.plot_date() does not return the lines it creates... by 
looking at matlab.plot_date(),  and comparing those with the case for 
regular plot() I think it should.. so we have a missing return statement..

-- 
Peter Groszkowski         Gemini Observatory
Tel: +1 808 974-2509      670 N. A'ohoku Place
Fax: +1 808 935-9235      Hilo, Hawai'i 96720, USA

>>>>> "Nils" == Nils Wagner <nw...@me...> writes:

    Nils> cvs -z3
    Nils> -d:pserver:ano...@cv...:/cvsroot/matplotlib
    Nils> co matplotlib cvs checkout: authorization failed: server
    Nils> cvs.sourceforge.net rejected access to /cvsroot/matplotlib
    Nils> for user anonymous

Hmm, I just tried anonymous access and got the same thing.
Sourceforge is flaky sometimes.  Let's give it a day and if the
problem persists I'll file a support request.

In the meantime, here's a link a current CVS snapshot:

http://nitace.bsd.uchicago.edu:8080/files/share/matplotlib-0.54.2a.tar.gz

JDH

cvs -z3 -d:pserver:ano...@cv...:/cvsroot/matplotlib co 
matplotlib
cvs checkout: authorization failed: server cvs.sourceforge.net rejected 
access to /cvsroot/matplotlib for user anonymous

>>>>> "Andrew" == Andrew Straw <str...@as...> writes:

    Andrew> Hi all, I'm trying to get some figures ready, but I've
    Andrew> encountered what may be a bug demonstrated by a trivial
    Andrew> program:


Yeah, it's a bug.  Replace the autoscale function in the Locator base
class, which currently raises the NotImplementedError, with

    def autoscale(self):
        'autoscale the view limits'
        self.verify_intervals()
        return self.dataInterval.get_bounds()

Should cure what ails you.

JDH

Hi all,

I'm trying to get some figures ready, but I've encountered what may be a 
bug demonstrated by a trivial program:

from matplotlib.matlab import *

set(gca(),'XTicks',[]) # fails
plot([1,2],[3,4])
#set(gca(),'XTicks',[]) # works
show()

The traceback is:

astraw@aspiring:~/src/py-play/matplotlib$ python no_ticks.py
Traceback (most recent call last):
  File "no_ticks.py", line 4, in ?
    plot([1,2],[3,4])
  File "/usr/lib/python2.3/site-packages/matplotlib/matlab.py", line 
1074, in plot
    try: lines =  gca().plot(*args, **kwargs)
  File "/usr/lib/python2.3/site-packages/matplotlib/axes.py", line 1361, 
in plot
    self.autoscale_view()
  File "/usr/lib/python2.3/site-packages/matplotlib/axes.py", line 426, 
in autoscale_view
    tup = self.xaxis.get_major_locator().autoscale()
  File "/usr/lib/python2.3/site-packages/matplotlib/ticker.py", line 
321, in autoscale
    raise NotImplementedError('Derived must override')
NotImplementedError: Derived must override

This trivial example works if I call set() after plot() although this is 
sometimes inconvenient.  Is this a bug or are there some intricacies I'm 
not aware of?

Cheers!
Andrew