Menu
▾
▴
Re: [Matplotlib-users] [matplotlib-devel] RFC: candidates for a new default colormap
|
From: Sourish B. <sou...@gm...> - 2015-06-05 18:39:10
|
<html>
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">On 06/05/2015 12:22 PM, Jody Klymak
wrote:<br>
</div>
<blockquote cite="mid:C4E...@uv..."
type="cite">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
Hi,
<div class=""><br class="">
<div>
<blockquote type="cite" class="">
<div class="">On 5 Jun 2015, at 11:17 AM, Sourish Basu <<a
moz-do-not-send="true"
href="mailto:sou...@gm..." class="">sou...@gm...</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<meta content="text/html; charset=utf-8"
http-equiv="Content-Type" class="">
<div bgcolor="#FFFFFF" text="#000000" class="">
<div class="moz-cite-prefix">On 06/05/2015 10:17 AM,
Jody Klymak wrote:<br class="">
</div>
<blockquote
cite="mid:EA9...@uv..."
type="cite" class="">
<meta http-equiv="Content-Type" content="text/html;
charset=utf-8" class="">
<div class="">Anyways, I guess I am advocating trying
to find a colormap with a very obvious central hue
to represent zero. Anomaly data sets are *very*
common, so having a default colormap that doesn’t do
something reasonable with them may be a turn off to
new users. <br class="">
</div>
</blockquote>
<br class="">
I agree that jet does a bad job with anomaly data, but I
disagree that having a diverging colormap as default (or
even a "diverging" argument to anything that takes a
cmap value) would solve that. 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).<br class="">
</div>
</div>
</blockquote>
<div><br class="">
</div>
<div>Well, I *strongly* disagree with that attached example!
It makes it look like -0.5 is equivalent to +1.5! Unless
there is a really strong reason to do that, I think that is
poor practice as it makes your negative anomalies look far
stronger than your positive, and that is not the case in the
underlying numbers.</div>
</div>
</div>
</blockquote>
<br>
Yes, that is indeed a problem. However, if I want to plot a field
which is mostly zeros, then I prefer to use a colormap which is
white at zero. I could just extend the smaller absolute value (-0.5)
to the same absolute value as the larger one, and plot -1.5 to 1.5.
But in that case, I'd only be using a third of the possible
dynamical range of the negative (blue) part, which IMO is a waste.
If I have a field which has a zero median (which I want mapped to
white), goes from -0.5 to +1.5, and I actually want to show the
difference between (say) -0.3 and -0.4, what other option do I have?<br>
<br>
This problem is reasonably common for me, BTW. I can have a carbon
monoxide field with an average/background of 60 ppb, but variations
from 30 to 550 ppb. So I need a color scale which (a) is white at
60, and (b) shows small variations below 60 and large variations
above 60 with equal "clarity".<br>
<br>
Cheers,<br>
Sourish<br>
<br>
<blockquote cite="mid:C4E...@uv..."
type="cite">
<div class="">
<div>
<div><br class="">
</div>
<div>Cheers, Jody</div>
<div><br class="">
</div>
<div><br class="">
</div>
<br class="">
<blockquote type="cite" class="">
<div class="">
<div bgcolor="#FFFFFF" text="#000000" class=""> OT, I
recently found a nice alternative to jet here: <a
moz-do-not-send="true" class="moz-txt-link-freetext"
href="https://mycarta.wordpress.com/2014/11/13/new-rainbow-colormap-sawthoot-shaped-lightness-profile/">https://mycarta.wordpress.com/2014/11/13/new-rainbow-colormap-sawthoot-shaped-lightness-profile/</a><br
class="">
It takes care of my biggest crib with jet, which is that
there is not enough perceptual variation in the middle
of the range.<br class="">
<br class="">
Cheers,<br class="">
Sourish Basu<br class="">
</div>
<span
id="cid:D73...@uv..."><ff_adjustment_winter.png></span>------------------------------------------------------------------------------<br
class="">
_______________________________________________<br
class="">
Matplotlib-users mailing list<br class="">
<a moz-do-not-send="true"
href="mailto:Mat...@li..."
class="">Mat...@li...</a><br
class="">
<a class="moz-txt-link-freetext" href="https://lists.sourceforge.net/lists/listinfo/matplotlib-users">https://lists.sourceforge.net/lists/listinfo/matplotlib-users</a><br
class="">
</div>
</blockquote>
</div>
<br class="">
<div apple-content-edited="true" class="">
<span class="Apple-style-span" style="border-collapse:
separate; border-spacing: 0px; color: rgb(0, 0, 0);
font-family: 'Lucida Sans Typewriter'; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
text-indent: 0px; text-transform: none; orphans: 2;
white-space: normal; widows: 2; word-spacing: 0px;">
<div class="">--</div>
<div class="">Jody Klymak </div>
<div class=""><a moz-do-not-send="true"
href="http://web.uvic.ca/%7Ejklymak/" class="">http://web.uvic.ca/~jklymak/</a></div>
<div class=""><br class="khtml-block-placeholder">
</div>
<div class=""><br class="khtml-block-placeholder">
</div>
<br class="Apple-interchange-newline">
</span><br class="Apple-interchange-newline">
</div>
<br class="">
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">------------------------------------------------------------------------------
</pre>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
Matplotlib-users mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Mat...@li...">Mat...@li...</a>
<a class="moz-txt-link-freetext" href="https://lists.sourceforge.net/lists/listinfo/matplotlib-users">https://lists.sourceforge.net/lists/listinfo/matplotlib-users</a>
</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
you if it misses the target.<br>
</div>
</body>
</html>
|
