Thread: Re: [Matplotlib-users] [matplotlib-devel] RFC: candidates for a new default colormap (Page 2)

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Re: [Matplotlib-users] [matplotlib-devel] RFC: candidates for a new default colormap

From: Benjamin R. <ben...@ou...> - 2015-06-05 20:46:22

Furthermore, I think there is some work being done to add functionality to
the Norm to allow specifying a middle value along with a vmin and a vmax.

Ben Root

On Fri, Jun 5, 2015 at 3:20 PM, Eric Firing <ef...@ha...> wrote:

> On 2015/06/05 8:17 AM, Sourish Basu wrote:
> > Very often the "zero" of an anomaly is not at the center of the extrema,
> > and requires creating a custom diverging colormap anyway (see attached
> > example).
>
> Reminder: in matplotlib, color mapping is done with the combination of a
> colormap and a norm.  This allows one to design a norm to handle the
> mapping, including any nonlinearity or difference between the handling
> of positive and negative values.  This is more general than customizing
> a colormap; once you have a norm to suit your purpose, you can use it
> with any colormap.
>
> Maybe this is actually what you are already doing, but I wanted to point
> it out here in case some readers are not familiar with this
> colormap+norm strategy.
>
> Eric
>
>
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>

Re: [Matplotlib-users] [matplotlib-devel] RFC: candidates for a new default colormap

From: Sourish B. <sou...@gm...> - 2015-06-05 21:43:45

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    <div class="moz-cite-prefix">On 06/05/2015 01:20 PM, Eric Firing
      wrote:
    </div>
    <blockquote cite="mid:557...@ha..." type="cite">
      <pre wrap="">
Reminder: in matplotlib, color mapping is done with the combination of a 
colormap and a norm.  This allows one to design a norm to handle the 
mapping, including any nonlinearity or difference between the handling 
of positive and negative values.  This is more general than customizing 
a colormap; once you have a norm to suit your purpose, you can use it 
with any colormap.

Maybe this is actually what you are already doing, but I wanted to point 
it out here in case some readers are not familiar with this 
colormap+norm strategy.</pre>
    </blockquote>
    <br>
    Actually, I didn't use norms because I never quite figured out how
    to use them or how to make my own. If there's a way to create a norm
    with a custom mid-point, I'd love to know/use that.<br>
    <br>
    -Sourish<br>
    <br>
    <blockquote cite="mid:557...@ha..." type="cite">
      <pre wrap="">

Eric

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</pre>
    </blockquote>
    <br>
    <br>
    <div class="moz-signature">-- <br>
      <b>Q:</b> What if you strapped C4 to a boomerang? Could this be an
      effective weapon, or would it be as stupid as it sounds?<br>
      <b>A:</b> Aerodynamics aside, I’m curious what tactical advantage
      you’re expecting to gain by having the high explosive fly back at
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Re: [Matplotlib-users] [matplotlib-devel] RFC: candidates for a new default colormap

From: Joe K. <jof...@gm...> - 2015-06-05 21:57:07

Not to plug one of my own answers to much, but here's a basic example.
http://stackoverflow.com/questions/20144529/shifted-colorbar-matplotlib

I've been meeting to submit a PR with a more full featured version for a
few years now, but haven't.
On Jun 5, 2015 4:45 PM, "Sourish Basu" <sou...@gm...> wrote:

>  On 06/05/2015 01:20 PM, Eric Firing wrote:
>
>
> Reminder: in matplotlib, color mapping is done with the combination of a
> colormap and a norm.  This allows one to design a norm to handle the
> mapping, including any nonlinearity or difference between the handling
> of positive and negative values.  This is more general than customizing
> a colormap; once you have a norm to suit your purpose, you can use it
> with any colormap.
>
> Maybe this is actually what you are already doing, but I wanted to point
> it out here in case some readers are not familiar with this
> colormap+norm strategy.
>
>
> Actually, I didn't use norms because I never quite figured out how to use
> them or how to make my own. If there's a way to create a norm with a custom
> mid-point, I'd love to know/use that.
>
> -Sourish
>
>
>
> Eric
>
> ------------------------------------------------------------------------------
> _______________________________________________
> Matplotlib-users mailing lis...@li...https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>
>
>
> --
> *Q:* What if you strapped C4 to a boomerang? Could this be an effective
> weapon, or would it be as stupid as it sounds?
> *A:* Aerodynamics aside, I’m curious what tactical advantage you’re
> expecting to gain by having the high explosive fly back at you if it misses
> the target.
>
>
> ------------------------------------------------------------------------------
>
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>
>

Re: [Matplotlib-users] [matplotlib-devel] RFC: candidates for a new default colormap

From: Sourish B. <sou...@gm...> - 2015-06-08 22:39:17

Attachments: JoeKington.py JoeKington.png

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    <div class="moz-cite-prefix"><br>
      On 06/05/2015 03:57 PM, Joe Kington wrote:<br>
    </div>
    <blockquote
cite="mid:CAC...@ma..."
      type="cite">
      <p dir="ltr">Not to plug one of my own answers to much, but here's
        a basic example. <a moz-do-not-send="true"
href="http://stackoverflow.com/questions/20144529/shifted-colorbar-matplotlib">http://stackoverflow.com/questions/20144529/shifted-colorbar-matplotlib</a></p>
      <p dir="ltr">I've been meeting to submit a PR with a more full
        featured version for a few years now, but haven't.</p>
    </blockquote>
    <br>
    This is great, but it has a slightly bothersome side effect on the
    colorbar ticks. In your original example, I changed the line 'data =
    10 * (data - 0.8)' to 'data = 10 * (data - 0.85)', so that the
    numbers are now in between -8.5 and +1.5. As a result, when the
    colorbar is drawn, you get a tick at -8, as well as one at -9
    (similarly at +1 and +2). Example attached. As in, the colorbar
    method seems intent on adding those tick marks at -9 and +2. The
    result is not aesthetically pleasing.<br>
    <br>
    In one of my real-data example, the minimum value of the data
    happened to be -4.003, and as a result there was a tick label at -4
    and an overlapping tick label at -5. Why does this happen only when
    I specify 'norm' in imshow? How do I get matplotlib to not do that?<br>
    <br>
    Thanks,<br>
    Sourish<br>
    <br>
    <blockquote
cite="mid:CAC...@ma..."
      type="cite">
      <div class="gmail_quote">On Jun 5, 2015 4:45 PM, "Sourish Basu"
        &lt;<a moz-do-not-send="true"
          href="mailto:sou...@gm...">sou...@gm...</a>&gt;
        wrote:<br type="attribution">
        <blockquote class="gmail_quote" style="margin:0 0 0
          .8ex;border-left:1px #ccc solid;padding-left:1ex">
          <div bgcolor="#FFFFFF" text="#000000">
            <div>On 06/05/2015 01:20 PM, Eric Firing wrote: </div>
            <blockquote type="cite">
              <pre>Reminder: in matplotlib, color mapping is done with the combination of a 
colormap and a norm.  This allows one to design a norm to handle the 
mapping, including any nonlinearity or difference between the handling 
of positive and negative values.  This is more general than customizing 
a colormap; once you have a norm to suit your purpose, you can use it 
with any colormap.

Maybe this is actually what you are already doing, but I wanted to point 
it out here in case some readers are not familiar with this 
colormap+norm strategy.</pre>
            </blockquote>
            <br>
            Actually, I didn't use norms because I never quite figured
            out how to use them or how to make my own. If there's a way
            to create a norm with a custom mid-point, I'd love to
            know/use that.<br>
            <br>
            -Sourish<br>
            <br>
            <blockquote type="cite">
              <pre>
Eric

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</pre>
            </blockquote>
            <br>
            <br>
            <div>-- <br>
              <b>Q:</b> What if you strapped C4 to a boomerang? Could
              this be an effective weapon, or would it be as stupid as
              it sounds?<br>
              <b>A:</b> Aerodynamics aside, I’m curious what tactical
              advantage you’re expecting to gain by having the high
              explosive fly back at you if it misses the target.<br>
            </div>
          </div>
          <br>
------------------------------------------------------------------------------<br>
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          Matplotlib-users mailing list<br>
          <a moz-do-not-send="true"
            href="mailto:Mat...@li...">Mat...@li...</a><br>
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            href="https://lists.sourceforge.net/lists/listinfo/matplotlib-users"
            target="_blank">https://lists.sourceforge.net/lists/listinfo/matplotlib-users</a><br>
          <br>
        </blockquote>
      </div>
    </blockquote>
    <br>
    <br>
    <div class="moz-signature">-- <br>
      <b>Q:</b> What if you strapped C4 to a boomerang? Could this be an
      effective weapon, or would it be as stupid as it sounds?<br>
      <b>A:</b> Aerodynamics aside, I’m curious what tactical advantage
      you’re expecting to gain by having the high explosive fly back at
      you if it misses the target.<br>
    </div>
  </body>
</html>

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