Thread: [Matplotlib-users] Colorbar Updates...

Hello NG,

    I haven't stated my question very clearly, probably. I 
am trying to use imshow() with a dinamically changing set of matrices.
What my application does, is just to respond to a user selection from 
awxPython radiobutton and, based on the user's choice, display a 
different matrix on a matplotlib figure (I am using the OO interface). 
I also have an horizontal colorbar to let the user orient himself over 
the matrix values. Well, these matrices have different magnitues in 
value, and I was expecting that the colorbar would be updated with the 
new image data. 
Isn't the colorbar supposed to update when the input 
image/pcolor/whatever changes?

I attach a modified example of 
dynamic_image_wxagg2.py that demonstrates the problem: the values in 
the image increase, but the colorbar stays quiet at its bounds 
(0.0,2.0) and ends up filled only with blue...

Does anyone have a 
suggestion?

Thank you.

Andrea.

Andrea,

  I agree, the colorbar should dynamically update.  A workaround might 
be to simply call colorbar every time you update the image data.

At least part of a longer-term solution may be to change colorbar so 
that instead of always using contourf, it uses imshow when it is being 
used with a nearly continuous set of colors instead of a small discrete set.

I have not had time to look at this closely, but I can add it to my list.

Eric

and...@ti... wrote:
> Hello NG,
> 
>     I haven't stated my question very clearly, probably. I 
> am trying to use imshow() with a dinamically changing set of matrices.
> What my application does, is just to respond to a user selection from 
> awxPython radiobutton and, based on the user's choice, display a 
> different matrix on a matplotlib figure (I am using the OO interface). 
> I also have an horizontal colorbar to let the user orient himself over 
> the matrix values. Well, these matrices have different magnitues in 
> value, and I was expecting that the colorbar would be updated with the 
> new image data. 
> Isn't the colorbar supposed to update when the input 
> image/pcolor/whatever changes?

Eric Firing wrote:
> Andrea,
> 
>  I agree, the colorbar should dynamically update.  A workaround might be 
> to simply call colorbar every time you update the image data.
> 
> At least part of a longer-term solution may be to change colorbar so 
> that instead of always using contourf, it uses imshow when it is being 
> used with a nearly continuous set of colors instead of a small discrete 
> set.
> 
> I have not had time to look at this closely, but I can add it to my list.
> 
> Eric
> 

Although updating the colorbar when the image data changes should be the 
default behaviour will there be a way to keep the colorbar from 
changing? I've got a visualization application where an image changes 
according to the position it's currently displaying but I want to keep 
the colorbar that reflects the largest value. Right now I just display 
first the image that has the largest value and the colorbar stays the 
same. Whatever the buggy behaviour an application has someone is taking 
advantage of it :-)

João Silva

It sounds like there are two questions here: whether the colorbar=20
correctly tracks the actual color mapping used in the image or contour=20
plot or whatever (it should always do this, but I think that at present=20
it does not), and whether the limits should change even if the mapping=20
does not.  I think the behavior you request is sensible, so that would=20
be my target, either as a standard behavior or as an option.  Thanks for=20
pointing out this aspect of the problem.

There is another problem with the colorbar code, and I have been trying=20
to decide how to handle that before looking at the update question, so I=20
have not resolved either one yet.

Eric

Jo=C3=A3o Lu=C3=ADs Silva wrote:
> Eric Firing wrote:
>=20
>> Andrea,
>>
>>  I agree, the colorbar should dynamically update.  A workaround might=20
>> be to simply call colorbar every time you update the image data.
>>
>> At least part of a longer-term solution may be to change colorbar so=20
>> that instead of always using contourf, it uses imshow when it is being=
=20
>> used with a nearly continuous set of colors instead of a small=20
>> discrete set.
>>
>> I have not had time to look at this closely, but I can add it to my li=
st.
>>
>> Eric
>>
>=20
> Although updating the colorbar when the image data changes should be th=
e=20
> default behaviour will there be a way to keep the colorbar from=20
> changing? I've got a visualization application where an image changes=20
> according to the position it's currently displaying but I want to keep=20
> the colorbar that reflects the largest value. Right now I just display=20
> first the image that has the largest value and the colorbar stays the=20
> same. Whatever the buggy behaviour an application has someone is taking=
=20
> advantage of it :-)
>=20
> Jo=C3=A3o Silva
>=20
>=20
>=20
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