color coding for numbers

[DJC]

On 21/08/12 12:55, Ulrich Eckhardt wrote:
> Am 21.08.2012 10:38, schrieb namenobodywants at gmail.com:
>> what is the best way
>
> Define "best" before asking such questions. ;)


<http://matplotlib.sourceforge.net/api/colors_api.html?highlight=colors#matplotlib.colors>
matplotlib.colors

A module for converting numbers or color arguments to RGB or RGBA

RGB and RGBA are sequences of, respectively, 3 or 4 floats in the range 0-1.

This module includes functions and classes for color specification 
conversions, and for mapping numbers to colors in a 1-D array of colors 
called a colormap.

see
<http://matplotlib.sourceforge.net/examples/pylab_examples/colours.html?highlight=colours>



>
>
>> using color/shading on a tkinter canvas as a visualization for a
>> two-dimensional grid of numbers? so far my best idea is to use the
>> same value for R,G and B (fill = '#xyxyxy'), which gives shades of
>> gray. if possible i'd like to have a larger number of visually
>> distinct values.
>
> The basic idea behind this is that you first normalize the values to a
> value between zero and one and then use that to look up an according
> color in an array. Of course you can also do both in one step or compute
> the colors in the array on the fly (like you did), but it helps keeping
> things simple at least for a start, and it also allows testing different
> approaches separately.
>
> If the different number of resulting colors isn't good enough then, it
> could be that the array is too small (its size determines the maximum
> number of different colours), that the normalization only uses a small
> range between zero and one (reducing the effectively used number of
> colours) or simply that your screen doesn't support that many different
> colors.
>
>
>  > i've seen visualizations that seem to use some kind
>  > of hot-versus-cold color coding. does anybody know how to do this?
>
> The colour-coding is just the way that above mentioned array is filled.
> For the hot/cold coding, you could define a dark blue for low values and
> a bright red for high values and then simply interpolate the RGB triple
> for values in between.
>
> Uli