[scilab-Users] heatmap / Matplot

[Joshua Auerbach]

Thanks for the info on grayplot.  A little confusing that something that 
plots colors would be called "gray"plot don't you think?

In any case, this almost gets me to where I want, except grayplot 
determines the color for each rectangle from the average value at each 
corner and I do not want this.  I want each rectangle to only take its 
color from one value (what is at the center of the rectangle).  ie if my 
z matrix is binary I want to only see two colors but with grayplot i 
will get a color for 0 (all four corners 0), 0.25 (one corner 1), 0.5 
(two corners 1), 0.75 (three corners 1) and 1 (all four corners 1).

Any advice on how to do that?

Thanks,
Josh

duboism at limsi.fr wrote:
> Hi Joshua,
>
> I think that the function grayplot (and its friends fgrayplot, Sgrayplot)
> would be useful for you but you will have to reformat your data.
>
> grayplot takes 3 arguments: x (vector of x coordinates, size nx), y
> (vector of y coordinates, size ny) and a nx*ny matrix data (the value at
> data(i,j) is the value of point (x(i), y(j)) ). See the script
> test_grayplot.sce.
>
> It should not be hard to re-format your data this way.
>
> Note the use of the zminmax option to plot different data with the same
> color scale (see test_grayplot2.sce).
> Note also that on the x86_64 architecture the function colorbar seems
> broken (in fact you cannot use it since it raises an error).
>
> Mathieu
>
>   
>> Hi,
>>
>> I am looking for some assistance.  I am trying to make what I know as a
>> heatmap.  Basically I have data for many points on a grid and want to
>> construct a 2d plot where each point is given a color on a gradient
>> (From blue to red say) based on the data value at that point.  I have
>> the data in the form of a matrix with 3 columns x-coord, y-coord, data
>> value
>>
>> Currently I am making this type of plot by transforming my grid
>> coordinates into matrix coordinates of a new matrix and scaling my data
>> values into the range [0, NUM_COLORS] and using the Matplot function to
>> plot this data.  This method does work, but has a few shortcomings: I
>> lose the original scale of my grid since the axis labels are based on
>> the matrix coordinates.  There is no key explaining the gradient and
>> even if there were I would lose the original scale of my data values.
>>
>> Does anyone know how to get around these limitations or know of a better
>> way to accomplish what I am trying to do?  I'd appreciate any help.
>>
>> Cheers,
>> Josh
>>
>>