matplotlib-users

[Matplotlib-users] Ploting a sparse matrix with imshow

[Jose G. <sjm...@go...>]

Dear matplotlib users,

I am trying to plot a nxn symetric matrix containing zeros (in white) 
and ones (in black). Quite simple, I guessed. For that I use imshow as 
follows:

 >>> imshow(W, cmap=cm.binary) # W is a Numpy Array with shape (100,100)

However, this does not work the way i would like (the ones appear very 
blur). I would need the correct representation of a grid where the 
possition 0,0 is simply the entry W[0,0] of my array.

There should be an easy way to plot this matrix, bu I cannot figure it out.

Thanks for your help in advance.

Jose

Re: [Matplotlib-users] Ploting a sparse matrix with imshow

[Eric F. <ef...@ha...>]

On 02/19/2012 10:18 AM, Jose Guzman wrote:
> Dear matplotlib users,
>
> I am trying to plot a nxn symetric matrix containing zeros (in white)
> and ones (in black). Quite simple, I guessed. For that I use imshow as
> follows:
>
>  >>> imshow(W, cmap=cm.binary) # W is a Numpy Array with shape (100,100)
>
> However, this does not work the way i would like (the ones appear very
> blur). I would need the correct representation of a grid where the
> possition 0,0 is simply the entry W[0,0] of my array.
>
> There should be an easy way to plot this matrix, bu I cannot figure it out.

Did you try matshow?

Eric

>
> Thanks for your help in advance.
>
> Jose
>
>
>
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Re: [Matplotlib-users] Ploting a sparse matrix with imshow

[Jeff W. <js...@fa...>]

On 2/19/12 1:18 PM, Jose Guzman wrote:
> Dear matplotlib users,
>
> I am trying to plot a nxn symetric matrix containing zeros (in white) 
> and ones (in black). Quite simple, I guessed. For that I use imshow as 
> follows:
>
> >>> imshow(W, cmap=cm.binary) # W is a Numpy Array with shape (100,100)
>
> However, this does not work the way i would like (the ones appear very 
> blur). I would need the correct representation of a grid where the 
> possition 0,0 is simply the entry W[0,0] of my array.
>
> There should be an easy way to plot this matrix, bu I cannot figure it 
> out.
>
> Thanks for your help in advance.
>
> Jose

Jose: I think you need to add interpolation='nearest' to get rid of the 
blurriness.

-Jeff

Re: [Matplotlib-users] Ploting a sparse matrix with imshow

[Jerzy K. <jer...@un...>]

Jeff Whitakert :
> Jose Guzman:
>> ...
>> >>> imshow(W, cmap=cm.binary) # W is a Numpy Array with shape (100,100)
>>
>> However, this does not work the way i would like (the ones appear 
>> very blur). I would need the correct representation of a grid where 
>> the possition 0,0 is simply the entry W[0,0] of my array.
>>
>
> Jose: I think you need to add interpolation='nearest' to get rid of 
> the blurriness.
A. This is one possibility.
B. The - mentioned previously - matshow, is another one.
C. figimage(W,cmap=cm.binary) is a third one ; here the scale is one to 
one in pixels, independently of the figsize.
D. Specific backend image plotting is yet another one, if somebody needs 
really to work hard.

Jerzy K.