How to generate a colourmap for a 2D denisty map?

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Cai Chin
Cai Chin 2020-11-17
评论： Cai Chin 2020-11-17
Hi, I am using MATLAB R2020a with a MacOS. I am currently trying to generate a colourmap to represent the density of points on the following plot:
I have used this function by Malcolm McLean to generate a density:
function [ dmap ] = dataDensity(x, y, width, height, limits, fudge)
if(nargin == 4)
limits(1) = min(x);
limits(2) = max(x);
limits(3) = min(y);
limits(4) = max(y);
end
deltax = (limits(2) - limits(1)) / width;
deltay = (limits(4) - limits(3)) / height;
if(nargin < 6)
fudge = sqrt(deltax^2 + deltay^2);
end
dmap = zeros(height, width);
for ii = 0: height - 1
yi = limits(3) + ii * deltay + deltay/2;
for jj = 0 : width - 1
xi = limits(1) + jj * deltax + deltax/2;
dd = 0;
for kk = 1: length(x)
dist2 = (x(kk) - xi)^2 + (y(kk) - yi)^2;
dd = dd + 1 / ( dist2 + fudge);
end
dmap(ii+1,jj+1) = dd;
end
end
end
I have used this function by Malcolm McLean to then generate a plot of this density.
function [ f ] = DataDensityPlot( x, y, levels )
map = dataDensity(x, y, 256, 256);
map = map - min(min(map));
map = floor(map ./ max(max(map)) * (levels-1));
f = figure();
image(map);
colormap(jet(levels));
set(gca, 'XTick', [1 256]);
set(gca, 'XTickLabel', [min(x) max(x)]);
set(gca, 'YTick', [1 256]);
set(gca, 'YTickLabel', [min(y) max(y)]);
uiwait;
end
However, this creates a contourmap as shown.
Instead, I would like to generate a plot where the colour directly corresponds to the density of points rather than having contours, similar to this:
I would very much appreciate suggestions on how to manipulate the function to create the desired colourmap. Thanks in advance

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采纳的回答

Cris LaPierre
Cris LaPierre 2020-11-17
编辑：Cris LaPierre 2020-11-17
Ran in:
It looks like your comparison image has had the color axis manually adjusted (rt click on colorbar and select "Interactive Colormap Shift"), but is either a hist3 or imagesc plot.
I'd be inclined to use hist3.
load v.mat
load w.mat
figure
hist3([v,w],'Nbins',[275 275],"EdgeColor","none",'CDataMode','auto')
view(2)
axis tight
colormap jet
caxis([0 250])
colorbar
●
  4 个评论
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Cris LaPierre
Cris LaPierre 2020-11-17
Rt click on colorbar and select "Interactive Colormap Shift", then position the cursor on the color bar and click and drag it to modify the color ranges. For example, I clicked on the green area and dragged it down to about 50.

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