matplotlib-users Mailing List for matplotlib

Thanks, I think cbar.ax.invert_yaxis() is what I am looking for.
Chao
On Sat, Nov 10, 2012 at 4:51 PM, Damon McDougall
<dam...@gm...>wrote:
> On Sat, Nov 10, 2012 at 9:41 AM, Paul Hobson <pmh...@gm...> wrote:
> > On Sat, Nov 10, 2012 at 7:07 AM, Chao YUE <cha...@gm...> wrote:
> >>
> >> Dear all,
> >>
> >> Is there a way to reverse the colorbar label, the default is small
> value at the bottom and big value at the top, yet I would like the big
> value at the bottom and small value at the top.
> >>
> >> all code in pylab mode.
> >>
> >> import numpy as np
> >> import matplotlib as mat
> >>
> >> a = np.arange(100).reshape(10,10)
> >> contourf(a,levels=np.arange(0,101,10))
> >> colorbar()
> >>
> >> in the above figure, colorbar label shows 0 at the bottom and 100 at
> the top.
> >> Yet I want the 0 at the top and the 100 at the bottom, with the same
> sequence of colors in the colorbar.
> >>
> >> One way is to reverse the cmap, and then reverse the colorbar labels at
> the same time:
> >> a = np.arange(100).reshape(10,10)
> >> contourf(a,levels=np.arange(0,101,10),cmap=mat.cm.jet_r)
> >> cbar = colorbar()
> >> cbar.set_ticks(np.arange(0,101,10))
> >> cbar.set_ticklabels(np.arange(100,-1,-10))
> >
> > Chao,
> >
> > I think it's as simple as:
> >
> > import numpy as np
> > import matplotlib.pyplot as plt
> >
> > a = np.arange(100).reshape(10,10)
> > fig, ax1 = plt.subplots()
> > CS = ax1.contourf(a,levels=np.arange(0,101,10))
> > cbar = plt.colorbar(CS)
> > cbar.ax.invert_yaxis()
> >
> > Does that produce the desired results?
> > -p
>
> Or, you could plot -a instead of a.
>
> --
> Damon McDougall
> http://www.damon-is-a-geek.com
> Institute for Computational Engineering Sciences
> 201 E. 24th St.
> Stop C0200
> The University of Texas at Austin
> Austin, TX 78712-1229
>
-- 
***********************************************************************************
Chao YUE
Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL)
UMR 1572 CEA-CNRS-UVSQ
Batiment 712 - Pe 119
91191 GIF Sur YVETTE Cedex
Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16
************************************************************************************

Thanks a lot Paul. Oh, I even didn't think about the second point raised by
you. but it would be great to have.
The main point is the first point raised by you, I just didn't know how to
put the label (in the example figure it's value range) exactly beside the
colorbar. In the attached figure you can see the labels (here the label is
a number) are put at the place of connection interface of two different
colors but not beside the colorbar. like for the first top blue block, I
would like to have 0-10 beside it, but not to put 0 at the top and 10 at
the bottom. I hope I am clear.
The code that generate attached figure is here:
 a = np.arange(100).reshape(10,10)
contourf(a,levels=np.arange(0,
101,10))
cbar = colorbar()
cbar.set_ticks(np.arange(0,101,10))
cbar.set_ticklabels(np.arange(0,101,10))
could you please indicate how can I have the first and second points raised
by you?
thanks a lot!
Chao
On Sat, Nov 10, 2012 at 4:53 PM, Paul Hobson <pmh...@gm...> wrote:
> On Sat, Nov 10, 2012 at 6:25 AM, Chao YUE <cha...@gm...> wrote:
> > Dear all,
> >
> > In the colorbar label for contourf or imshow plot, I want the effect like
> > that in the attached figure. Is there some way to move the position of
> > colorbar label? could someone give any hints?
>
>
> Chao,
>
> It's not clear what you mean. What's distinctive about the image you
> attached? Is it:
> - The ranges of values listed to the side?
> - The discrete blocks for each value range?
> - The units being listed above the colorbar?
>
> I think I can help you do any of those things. I just need to know
> what you're specifically trying to do.
> -paul
>
-- 
***********************************************************************************
Chao YUE
Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL)
UMR 1572 CEA-CNRS-UVSQ
Batiment 712 - Pe 119
91191 GIF Sur YVETTE Cedex
Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16
************************************************************************************

On Sat, Nov 10, 2012 at 6:25 AM, Chao YUE <cha...@gm...> wrote:
> Dear all,
>
> In the colorbar label for contourf or imshow plot, I want the effect like
> that in the attached figure. Is there some way to move the position of
> colorbar label? could someone give any hints?
Chao,
It's not clear what you mean. What's distinctive about the image you
attached? Is it:
- The ranges of values listed to the side?
- The discrete blocks for each value range?
- The units being listed above the colorbar?
I think I can help you do any of those things. I just need to know
what you're specifically trying to do.
-paul

On Sat, Nov 10, 2012 at 9:41 AM, Paul Hobson <pmh...@gm...> wrote:
> On Sat, Nov 10, 2012 at 7:07 AM, Chao YUE <cha...@gm...> wrote:
>>
>> Dear all,
>>
>> Is there a way to reverse the colorbar label, the default is small value at the bottom and big value at the top, yet I would like the big value at the bottom and small value at the top.
>>
>> all code in pylab mode.
>>
>> import numpy as np
>> import matplotlib as mat
>>
>> a = np.arange(100).reshape(10,10)
>> contourf(a,levels=np.arange(0,101,10))
>> colorbar()
>>
>> in the above figure, colorbar label shows 0 at the bottom and 100 at the top.
>> Yet I want the 0 at the top and the 100 at the bottom, with the same sequence of colors in the colorbar.
>>
>> One way is to reverse the cmap, and then reverse the colorbar labels at the same time:
>> a = np.arange(100).reshape(10,10)
>> contourf(a,levels=np.arange(0,101,10),cmap=mat.cm.jet_r)
>> cbar = colorbar()
>> cbar.set_ticks(np.arange(0,101,10))
>> cbar.set_ticklabels(np.arange(100,-1,-10))
>
> Chao,
>
> I think it's as simple as:
>
> import numpy as np
> import matplotlib.pyplot as plt
>
> a = np.arange(100).reshape(10,10)
> fig, ax1 = plt.subplots()
> CS = ax1.contourf(a,levels=np.arange(0,101,10))
> cbar = plt.colorbar(CS)
> cbar.ax.invert_yaxis()
>
> Does that produce the desired results?
> -p
Or, you could plot -a instead of a.
-- 
Damon McDougall
http://www.damon-is-a-geek.com
Institute for Computational Engineering Sciences
201 E. 24th St.
Stop C0200
The University of Texas at Austin
Austin, TX 78712-1229

On Sat, Nov 10, 2012 at 7:07 AM, Chao YUE <cha...@gm...> wrote:
>
> Dear all,
>
> Is there a way to reverse the colorbar label, the default is small value at the bottom and big value at the top, yet I would like the big value at the bottom and small value at the top.
>
> all code in pylab mode.
>
> import numpy as np
> import matplotlib as mat
>
> a = np.arange(100).reshape(10,10)
> contourf(a,levels=np.arange(0,101,10))
> colorbar()
>
> in the above figure, colorbar label shows 0 at the bottom and 100 at the top.
> Yet I want the 0 at the top and the 100 at the bottom, with the same sequence of colors in the colorbar.
>
> One way is to reverse the cmap, and then reverse the colorbar labels at the same time:
> a = np.arange(100).reshape(10,10)
> contourf(a,levels=np.arange(0,101,10),cmap=mat.cm.jet_r)
> cbar = colorbar()
> cbar.set_ticks(np.arange(0,101,10))
> cbar.set_ticklabels(np.arange(100,-1,-10))
Chao,
I think it's as simple as:
import numpy as np
import matplotlib.pyplot as plt
a = np.arange(100).reshape(10,10)
fig, ax1 = plt.subplots()
CS = ax1.contourf(a,levels=np.arange(0,101,10))
cbar = plt.colorbar(CS)
cbar.ax.invert_yaxis()
Does that produce the desired results?
-p

Hi, I once was indicated a way to extract colors from exsiting colormaps:
I just answered a question on Stackoverflow and maybe you can have a look.
all code in pylab mode
a = np.arange(100).reshape(10,10)
#here is the image with white and black end
imshow(a,cmap=mat.cm.binary)
colorbar()
#we extract only the 0.2-->0.7 part of original colormap and make a new one
#so that the white and black end are removed
rgba_array = mat.cm.binary(np.linspace(0,1,num=10,endpoint=True))
extract_rgba_array_255 = rgba_array[2:8,0:3]
imshow(a,cmap=mat.colors.ListedColormap(extract_rgba_array_255))
colorbar()
cheers,
Chao
--
View this message in context: http://matplotlib.1069221.n5.nabble.com/colormap-shift-tp39660p39707.html
Sent from the matplotlib - users mailing list archive at Nabble.com.

Dear all,
Is there a way to reverse the colorbar label, the default is small value at
the bottom and big value at the top, yet I would like the big value at the
bottom and small value at the top.
all code in pylab mode.
import numpy as np
import matplotlib as mat
a = np.arange(100).reshape(10,10)
contourf(a,levels=np.arange(0,101,10))
colorbar()
in the above figure, colorbar label shows 0 at the bottom and 100 at the
top.
Yet I want the 0 at the top and the 100 at the bottom, with the same
sequence of colors in the colorbar.
One way is to reverse the cmap, and then reverse the colorbar labels at the
same time:
a = np.arange(100).reshape(10,10)
contourf(a,levels=np.arange(0,101,10),cmap=mat.cm.jet_r)
cbar = colorbar()
cbar.set_ticks(np.arange(0,101,10))
cbar.set_ticklabels(np.arange(100,-1,-10))
But the problem is, sometimes I used the customized colormap, and to
increase the contrast, I do linear transformation for the data before I
plot them.
The the data that are really used for plotting are not the same. But in the
colorbar label, I used the values before transformation. Is this
complicated case,
reverse the customized colormap could not solve the problem (unlike in the
simple example above.) Does anyone have the same experience?
Thanks et cheers,
Chao
-- 
***********************************************************************************
Chao YUE
Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL)
UMR 1572 CEA-CNRS-UVSQ
Batiment 712 - Pe 119
91191 GIF Sur YVETTE Cedex
Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16
************************************************************************************

Dear all,
In the colorbar label for contourf or imshow plot, I want the effect like
that in the attached figure. Is there some way to move the position of
colorbar label? could someone give any hints?
Thanks!
Chao
-- 
***********************************************************************************
Chao YUE
Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL)
UMR 1572 CEA-CNRS-UVSQ
Batiment 712 - Pe 119
91191 GIF Sur YVETTE Cedex
Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16
************************************************************************************