matplotlib-users Mailing List for matplotlib

I would like to make biplot for principal component analysis with data
values scale on left and bottom and loadings values scale on right and top.
If I try to do it like that:
    ax2 = ax1.twinx().twiny()

I can plot data correctly (data on ax1 and loadings on ax2), but I have to
turn y axis on ax2 off (ax2.yaxis.set_visible(False)) that I don't have
double scale on the left and bottom scale is not the same as I set it with
ax1.axis() anymore. Is there another way to do it? I would also like to
change color of tick labels on upper and right scale (currently I can do it
only with upper scale).

Nejc

Andrew Kelly wrote:
> I am currently using the annotate() method for my data points and I 
> was curious if there is a way to center a line of text relative to a 
> line of text below it.  I am currently using two annotate() function 
> calls in a row (I need the text to be different colors) but I need the 
> first one to act as a title for the second (i.e. so I want it centered 
> relative to the one below.)  I have tried to use the length of the 
> second bit of text to center but I just cannot seem to do it.  The 
> code looks sort of like this:
>
> import matplotlib.pyplot as plt
> .......
> annotateTitle='Title'
> annotateText='Blah, Blah, Blah'
> plt.annotate(annotateTitle, xy=(1,1), xytext=(20,50), xycoords='data', 
> textcoords='offset points')
> plt.annotate(annotateText, xy=(1,1), xytext=(20,20), xycoords='data', 
> textcoords='offset points', size='small', color='black')
>


In the example at the bottom of 
http://matplotlib.sourceforge.net/users/annotations.html

you see an example where the horizontalalignment is specified.  Can you 
just do something like the following?


plt.annotate(annotateTitle, xy=(1,1), xytext=(20,50), xycoords='data', 
textcoords='offset points', horizontalalignment='center')
plt.annotate(annotateText, xy=(1,1), xytext=(20,20), xycoords='data', 
textcoords='offset points', size='small', color='black', 
horizontalalignment='center')


You also see examples of the alignment parameters at 
http://matplotlib.sourceforge.net/examples/pylab_examples/annotation_demo.html#pylab-examples-annotation-demo

Thanks,

Jason

Jeff,
Ok, so this is what I was trying to achieve...

c=['#6C9F7B','#783F68','#F4F4F2','#22F322','#F3F322','#0000F3']
mycm=mpl.colors.LinearSegmentedColormap.from_list('mycm',c)
plt.imshow(rand(10,10),cmap=mycm,interpolation='nearest')
colorbar()
plt.show()

That was the initial goal; being able to quickly create the cmap based on
some basic colors.
from there, I can optionally play with the mycm._segmentdata dictionary in
order to fine-tune the color spread.

...the documentation on the 'LinearSegmentedColormap.from_list()' method is
very brief, 
and there wasn't an example, so I didn't see it right away...

Anyway, problem solved.
Sorry for the confusion, & thanks again for the help

P.Romero

-----Original Message-----
From: Jeff Whitaker [mailto:js...@fa...] 
Sent: 2009-08-14 6:35 PM
To: P.R.
Subject: Re: [Matplotlib-users] colormap creation

P.R. wrote:
> Jeff,
> Thanks for pointing me to that example.
> I was basically manually performing the same operations as those listed in
> the example.
> however, like I said before, its been slow going, since I have to manually
> edit the ranges & adjust 'linear spread' of each color.
> It's a trial & error process...
>
> Im clear on how the rgb dictionary works; 
> I guess my problem/question was more on how to automate some of the work
> involved in creating the rgb dictionary.
>
> Example:
> Supposing that I have a rough idea of what color sequence I want, 
> let's say, 
>
> black 
> blue
> yellow
> red
> purple
>
> ... yet Im not sure about the exact values or 'tones' of these colors... 
> (this is an arbitrary example, let's assume that a similar cmap doesn't
> already exist in mpl)
>
> - I'd like to have an automatic method to easily create a preliminary,
> 'rough draft' rgb dictionary based on the rgb values for my basic
colors... 
> this way, I can quickly create a 'prototype' dictionary that I can then
> modify & adjust to suit my needs.
>
> so, a 'colormap generator' that takes a set of rgb values as input, and
> create the value ranges within the rgb dictionary automatically...
>
> Any ideas?
>   

Nope, sorry. 

-Jeff
> Thanks,
> P.Romero
>
> -----Original Message-----
> From: Jeff Whitaker [mailto:js...@fa...] 
> Sent: 2009-08-14 5:29 PM
> To: P.R.
> Cc: mat...@li...
> Subject: Re: [Matplotlib-users] colormap creation
>
> P.R. wrote:
>   
>> Can someone please recommend a (semi) automatic way to create the rgb
>> dictionaries needed for colormap creation?
>> Basically, I have a 'general' idea of how I want my colors ordered, but
Im
>> finding it difficult to create the smooth transitions by manually editing
>> the rgb dictionary for my custom colormap...the trial & error process is
>> tedious & not very accurate...
>>
>> How were the matplotlib colormaps created?
>> Were they created manually or programmatically?
>> Was it done using a random color selection?
>>
>> Please help,
>> Thanks,
>> P.Romero
>>   
>>     
>
> P.R.:  If you haven't already, you should look at the custom_cmap.py 
> example.
>
> -Jeff
>
>   


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