Color scale of scatter plot?

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Martina Bonsignore
Martina Bonsignore on 29 Nov 2021
Commented: Mathieu NOE on 30 Nov 2021
Hi! That's my problem: I have datas like this images, the red dot is a wheater station, the blue dots are lightnings, in the axies there are the lat/lon coordinates.
For each lightning I have associated a value (weight) that decrease from the station (in correspondence of this point there is 1) to the the farthest lightning ( ~0). I need that the colour of the dots changes gradually from dark blue (near the station) to light blue (the farthest lightning).
The matrix of the data is 1480x4 (first column -> datenum of the lightning, second and third columns -> coordinates, fourth column -> weight value of the lightning).
The actual code is:
scatter(longitude_lightnings,latitude_lightnings,6,'filled')
scatter(longitude_station,latitude_station,'filled')
Someone can help me? Thanks!

Accepted Answer

Mathieu NOE
Mathieu NOE on 29 Nov 2021
hello
A minor variation on the above suggestion
% dummy data
N = 100;
Xc = 5; % center X coordinate
Yc = 5; % center Y coordinate
X = randn(N,1)+Xc;
Y = randn(N,1)+Yc;
dist = sqrt((X-Xc).^2 + (Y-Yc).^2);
[weight,ind] = sort(dist,'ascend');
X = X(ind);
Y = Y(ind);
% light to dark blue colormap
n=256; % number of colors
cmap = [linspace(.9,0,n)', linspace(.9447,.447,n)', linspace(.9741,.741,n)']; % light to dark blue colormap
cmap_inverted = flip(cmap); % now dark to light blue
S = (weight-min(weight))/(max(weight)-min(weight))*(n-1)+1; % map to n colors
scatter(Xc,Yc,'r', 'filled');hold on
scatter(X,Y,[],S, 'filled');hold off
colormap(cmap_inverted)
hcb=colorbar('ver'); % colorbar handle
hcb.FontSize = 12;
hcb.Title.String = "Range";
hcb.Title.FontSize = 15;

More Answers (1)

Chunru
Chunru on 29 Nov 2021
x = randn(100, 1);
y = randn(100, 1);
cmap = parula(512);
cmap = cmap(1:360, :); % dark blue to green (360 colors)
pos_station = [0 0];
c = sqrt((x-pos_station(1)).^2 + (y-pos_station(2)).^2);
c = (c-min(c))/(max(c)-min(c))*359+1; % map to 360 colors
scatter(x,y,[],c, 'filled');
colormap(cmap)
colorbar

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R2020b

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