matplotlib-users Mailing List for matplotlib

Flavio,

One more point: please do not use quiver2 directly.  Instead, use 
quiver, which will call quiver2 unless it finds a keyword argument that 
exists only in the old version of quiver.  The name quiver2 is used only 
temporarily to provide this compatibility, which will be removed in a 
future release.

Eric

Flavio Coelho wrote:
> Hi,
> 
> I am tring to figure out how to use the c argument to the quiver2 function.

Thanks Eric,

in fact it depends on if x,y are 0 or not. But I got it to work it now.

thanks,

Fl=E1vio

On 8/22/06, Eric Firing <ef...@ha...> wrote:
>
> Flavio Coelho wrote:
> > Hi,
> >
> > I am tring to figure out how to use the c argument to the quiver2
> function.
> >
> > I want to be able to color my arrows proportionally to their size.
> >
> > I have tried this and it doesn' t work as I imagined:
> >
> > c =3D sqrt((array(u)-array(x))**2+(array(v)-array(y))**2)
>
> The length of the arrow is proportional to sqrt(u**2 + v**2),
> not to sqrt((u-x)**2 + (v-y)**2).
>
> Is the reason you are not getting what you expect?
>
> Eric
>
> >
> > quiver2(x,y,u,v,c)
> >
> > the docstring on quiver2 is not clear on how c works, any help will be
> > appreciated.
>



--=20
Fl=E1vio Code=E7o Coelho
registered Linux user # 386432
---------------------------
"Laws are like sausages. It's better not to see them being made."
Otto von Bismark

Flavio Coelho wrote:
> Hi,
> 
> I am tring to figure out how to use the c argument to the quiver2 function.
> 
> I want to be able to color my arrows proportionally to their size.
> 
> I have tried this and it doesn' t work as I imagined:
> 
> c = sqrt((array(u)-array(x))**2+(array(v)-array(y))**2)

The length of the arrow is proportional to sqrt(u**2 + v**2),
not to sqrt((u-x)**2 + (v-y)**2).

Is the reason you are not getting what you expect?

Eric

> 
> quiver2(x,y,u,v,c)
> 
> the docstring on quiver2 is not clear on how c works, any help will be 
> appreciated.

Phil, Jim,

Thanks.  I need to add a suitable example for the contourf case, because 
as you have discovered it is a little different from all the other 
mappable cases: colorbar takes its cue from the contourf arguments so as 
to be consistent with the way the contourf plot was made.  There is a 
line in the colorbar docstring indicating this, although I don't recall 
when I put that line in, so it may not be in the version you are using:

If mappable is a ContourSet, its extend kwarg is included automatically.

Eric

Philip Austin wrote:
> James Boyle writes:
>  > Thanks, Eric
>  > 
>  > to
>  > 
>  > im = contourf(Zm,cmap=palette)
>  > 
>  > I do not get the over/under pointers on the end of the colorbar.
>  > 
>  > Does this feature not work with contourf - Or am I doing something 
>  > wrong.
> 
> Here's a code segment that works for me:
> 
>     vmin,vmax=(280,305)
>     norm = colors.normalize(vmin = vmin, vmax = vmax, clip = True)
>     cmap=matplotlib.cm.jet
>     cmap.set_over('salmon', 1.0)
>     cmap.set_under('black', 0.25)
>     contplot = axes.contourf(pv.time_value,
>                              pv.pressure_value,
>                              pv.var1_value,
>                              n.arange(vmin,vmax,2.),
>                              norm=norm,
>                              extend='both',
>                              cmap=cmap)
> 
> 
> I got the hint on this from the contourf docstring
> 
>         ***** New: *****
>         * extend = 'neither', 'both', 'min', 'max'
>           Unless this is 'neither' (default), contour levels are
>           automatically added to one or both ends of the range so that
>           all data are included.  These added ranges are then
>           mapped to the special colormap values which default to
>           the ends of the colormap range, but can be set via
>           Colormap.set_under() and Colormap.set_over() methods.
>           To replace clip_ends=True and V = [-100, 2, 1, 0, 1, 2, 100],
>           use extend='both' and V = [2, 1, 0, 1, 2].
> 
> 
> regards, Phil
> 
> 
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I was a little suprised to learn that

axes.toggle_log_lineary()

overwrites user-supplied tick locators and formatters.  My naive
assumption was that it would "toggle" only the semilog property
and leave other attributes unchanged.  Perhaps this could be
mentioned in the docstring?

regards, Phil Austin

James Boyle writes:
 > Thanks, Eric
 > 
 > to
 > 
 > im = contourf(Zm,cmap=palette)
 > 
 > I do not get the over/under pointers on the end of the colorbar.
 > 
 > Does this feature not work with contourf - Or am I doing something 
 > wrong.

Here's a code segment that works for me:

    vmin,vmax=(280,305)
    norm = colors.normalize(vmin = vmin, vmax = vmax, clip = True)
    cmap=matplotlib.cm.jet
    cmap.set_over('salmon', 1.0)
    cmap.set_under('black', 0.25)
    contplot = axes.contourf(pv.time_value,
                             pv.pressure_value,
                             pv.var1_value,
                             n.arange(vmin,vmax,2.),
                             norm=norm,
                             extend='both',
                             cmap=cmap)


I got the hint on this from the contourf docstring

        ***** New: *****
        * extend = 'neither', 'both', 'min', 'max'
          Unless this is 'neither' (default), contour levels are
          automatically added to one or both ends of the range so that
          all data are included.  These added ranges are then
          mapped to the special colormap values which default to
          the ends of the colormap range, but can be set via
          Colormap.set_under() and Colormap.set_over() methods.
          To replace clip_ends=True and V = [-100, 2, 1, 0, 1, 2, 100],
          use extend='both' and V = [2, 1, 0, 1, 2].


regards, Phil

Thanks, Eric

Ok,
I ran the image_masked.py and all went OK
BUT
if I change line 34 of image_masked.py:
im = imshow(Zm, interpolation='bilinear',
     cmap=palette,
     norm = colors.normalize(vmin = -1.0, vmax = 1.0, clip = False),
     origin='lower', extent=[-3,3,-3,3])

to

im = contourf(Zm,cmap=palette)

I do not get the over/under pointers on the end of the colorbar.

Does this feature not work with contourf - Or am I doing something 
wrong.

--Jim

On Aug 21, 2006, at 5:13 PM, Eric Firing wrote:

> Jim,
>
> Look at examples/image_masked.py.  I think that is the only example 
> with pointed ends, and I think it was present as-is in 0.87.3.
>
> Eric
>
> James Boyle wrote:
>> I am using matplotlib 0.87.3
>> The documentation of colorbar in color.py seems to indicate that one 
>> should be able to create a color bar with pointed ends, the fill 
>> color of the ends corresponding to the over and under colors.
>> I have not been able to get this to work.  I have set the 
>> colormap.set_under and set_over values but no success.
>> If this does work could someone (Eric?) post an example, of how it is 
>> done. I feel that I am missing something simple.
>> Thanks for any help.
>> --Jim

Hi,

I am tring to figure out how to use the c argument to the quiver2 function.

I want to be able to color my arrows proportionally to their size.

I have tried this and it doesn' t work as I imagined:

c =3D sqrt((array(u)-array(x))**2+(array(v)-array(y))**2)

quiver2(x,y,u,v,c)

the docstring on quiver2 is not clear on how c works, any help will be
appreciated.

thanks,
--=20
Fl=E1vio Code=E7o Coelho
registered Linux user # 386432
---------------------------
"Laws are like sausages. It's better not to see them being made."
Otto von Bismark

> The colors come from the current colormap.  You can go all out and
>  make your own colormap and color based on index using your map.  I
>  don't know how to do that off the top of my head though.

The colors may come from the colormap, but how do they get assigned to
areas of the plot itself?  The most obvious way to do it is to index
by z, so areas with low z are shown with a cool color, and areas with
high z are shown with a hot color (assuming you are using a cold-hot
colormap).

As far as I can tell though, this is not the system currently used,
nor is there any coherent system used.

array.tolist() can be used as a temporary workaround.
i.e.  tack .tolist() onto the end of any numpy.array arguments to matplotlib
functions.

--bb

On 8/22/06, Sven Schreiber <sve...@gm...> wrote:
>
> Hi all,
>
> I'm using recently changed numpy features, so I have not been able to
> use matplotlib in a while, hoping for a release compatible with numpy
> 1.0beta.
>
> I guess I could also install Numeric and use that for matplotlib in the
> meantime, as a workaround. But from posts on the devel list it seems
> that a new release is imminent?
>
> It's just that I need to get something done in matplotlib until
> tomorrow, so it would be great if somebody could tell me if I should
> workaround or just wait.
>
> Btw, I tried the egg that was mentioned in a post, but it didn't work
> for me (something about "matrix not defined" or similar).
>
> Thanks for your help,
> Sven
>
>

Hi,
I have come across a couple of bugs when zooming into a plot

1) if you goto draw a box (to where you are going to zoom) it will zoom in
fine
but if while drawing the box you release the mouse button BUT continue to
move the mouse the zoom does not function (when mouse stops) and a black box
is drawn in the plotting window

2) If you just keep zooming in eventually you get to a point where the graph
just doesn't make sense.
I mean if you plot a slope and keep zooming in smaller and smaller you
eventually get to a position where you suddenly get a "triangle" shaped plot

Hi all,

I'm using recently changed numpy features, so I have not been able to
use matplotlib in a while, hoping for a release compatible with numpy
1.0beta.

I guess I could also install Numeric and use that for matplotlib in the
meantime, as a workaround. But from posts on the devel list it seems
that a new release is imminent?

It's just that I need to get something done in matplotlib until
tomorrow, so it would be great if somebody could tell me if I should
workaround or just wait.

Btw, I tried the egg that was mentioned in a post, but it didn't work
for me (something about "matrix not defined" or similar).

Thanks for your help,
Sven

"Derek Hohls" <DH...@cs...> writes:

>   In [9]: ax.set_xlim()?
>  I get
>   Object `ax.set_xlim()` not found.

You need to do ax.set_xlim? without the parentheses.

> You suggested:
> "The list you want is precisely the output of the getp command."
> But for the getp? , I get:

I meant the output of the actual getp command, not its help text. E.g.

    In [4]:recs=bar([1,2,3],[4,5,6])

    In [5]:getp(recs)
        alpha = 1.0
        animated = False
          ...
        y = 0.0
        zorder = 1

gives you the list of properties settable with setp. Similarly
getp(gca()) gives you a long list of properties, including xticklines.

> The matplotlabprc file has a clearly labelled line that 
> addresses part of this:
>  
> xtick.major.size     : 2      # major tick size in points
>  
> but of course I would like to do this in code.

I guess it isn't very obvious how to do this with setp. It is the
markersize property (which has the abbreviation ms):

    In [25]:setp(getp(gca(), 'xticklines'), 'ms', 10)

Note that here getp returns a list of objects, and setp sets the
property on every object in the list.

But if you already know what something is called in the matplotlibrc
file, you can set it programmatically:

    In [49]:rc('xtick.major', size=5, pad=20)

The rc settings do not affect existing images, so you have to make a
new plot before you see the effect:

    In [50]:figure(); bar([1,2,3],[4,5,6])

> I guess that, overall, I have been expecting matplotlib to
> have a simple "dot" notation throughout - 
>   xaxis.xtick.major.size = 2

The getp/setp methods are part of matplotlib's pylab interface, which
is designed to reproduce Matlab's "handle graphics". There is also an
OO interface, which looks like this (this is the agg_oo.py example
from the examples subdirectory):

    fig = Figure()
    canvas = FigureCanvas(fig)
    ax = fig.add_subplot(111)
    ax.plot([1,2,3])
    ax.set_title('hi mom')
    ax.grid(True)
    ax.set_xlabel('time')
    ax.set_ylabel('volts')
    canvas.print_figure('test')

I seem to recall some discussion about making it more Pythonic, e.g. 
allowing you to do

    ax.title = 'hi mom'
    ax.xlabel = 'time'

but I don't know whether it is a high priority for any of the
developers.

-- 
Jouni

The colors come from the current colormap.  You can go all out and
make your own colormap and color based on index using your map.  I
don't know how to do that off the top of my head though.

On 8/21/06, rich kowalczyk <ric...@gm...> wrote:
> I understand that 3D plotting is not fully working yet, but I have a
> question that might be answerable anyway.
>
> I can get a nice looking 3D plot of my data using
>
> surf = ax3d.plot_surface(x, y, z)
>
> but I can't control the colors used in the plot.  I can do a
>
> surf.set_array(ColorArray)
>
> and the contents of the array (ColorArray) will be translated into
> colors on the plot somehow, but the translation appears to be
> arbitrary.  Does anyone know how the translation is done, so that I
> can assign a certain color to a certain part of the plot?
>
> Thanks,
> Rich.
>
> -------------------------------------------------------------------------
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>

I understand that 3D plotting is not fully working yet, but I have a
question that might be answerable anyway.

I can get a nice looking 3D plot of my data using

surf = ax3d.plot_surface(x, y, z)

but I can't control the colors used in the plot.  I can do a

surf.set_array(ColorArray)

and the contents of the array (ColorArray) will be translated into
colors on the plot somehow, but the translation appears to be
arbitrary.  Does anyone know how the translation is done, so that I
can assign a certain color to a certain part of the plot?

Thanks,
Rich.

Jim,

Look at examples/image_masked.py.  I think that is the only example with 
pointed ends, and I think it was present as-is in 0.87.3.

Eric

James Boyle wrote:
> I am using matplotlib 0.87.3
> 
> The documentation of colorbar in color.py seems to indicate that one 
> should be able to create a color bar with pointed ends, the fill color 
> of the ends corresponding to the over and under colors.
> 
> I have not been able to get this to work.  I have set the 
> colormap.set_under and set_over values but no success.
> 
> If this does work could someone (Eric?) post an example, of how it is 
> done. I feel that I am missing something simple.
> 
> Thanks for any help.
> 
> --Jim
> 
> 
> -------------------------------------------------------------------------
> Using Tomcat but need to do more? Need to support web services, security?
> Get stuff done quickly with pre-integrated technology to make your job easier
> Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
> http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
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