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How to plot scatter graph with colourmap functon

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Hi,
I have this 3 column matrix, where:
column 1 = x values
column 2 = y values
columnn 3 = value of each given point
myVal = [0 21 1.07 ;
0 60 0.51 ;
0 81 0.74 ;
0 102 0.84 ;
0 151 0.96 ;
0 201 1.26 ;
0 300 1.08 ;
0 387 1.31 ;
0 501 1.44 ;
0 589 1.4 ;
0 693 1.39 ;
0 792 1.25 ;
0 889 1.16 ;
0 990 1.07 ;
0 1185 1.21 ;
0 1384 1.14 ;
0 1582 1.44 ;
0 1778 1.42 ;
0 1976 0.69 ;
0 2466 1.04 ;
0 2957 1.64 ;
0 3201 0.94 ;
0 3521 0.82 ;
48.8 19 1.01 ;
48.8 37 0.37 ;
48.8 50 0.47 ;
48.8 75 0.63 ;
48.8 99 0.75 ;
48.8 119 0.57 ;
48.8 137 3.04 ;
74.8 21 0.73 ;
74.8 39 0.34 ;
74.8 71 0.52 ;
74.8 149 0.6 ;
74.8 200 0.89 ;
74.8 300 0.56 ;
74.8 398 0.74 ;
74.8 496 0.81 ;
74.8 596 0.86 ;
74.8 694 1.03 ;
74.8 792 0.85 ;
282.7 15 0.12 ;
282.7 54 0.19 ;
282.7 80 0.18 ;
282.7 100 0.24 ;
282.7 199 0.29 ;
282.7 497 0.56 ;
282.7 695 0.76 ];
How would I adapt this data to work for this scatter heatmap function:
cmap = jet(256); %state colourmaop
v = rescale(myVal, 1, 256);
numVal = length(myVal)
markerColors = zeros(numVal, 3)
% Now assign marker colors according to the value of the data.
for k = 1 : numVal
row = round(v(k));
markerColors(k, :) = cmap(row, :);
end
% Create the scatter plot.
scatter(x, y, [], markerColors);
grid on;
Charlie

  3 Comments

KSSV
KSSV on 3 Dec 2020
x = myVal(:,1) ;
y = myVal(:,2) ;
z = myVal(:,3) ;
scater(x,y,[],z,'filled')
colorbar
Charlie Hillary
Charlie Hillary on 3 Dec 2020
Ok. I get this error 'Index in position 2 exceeds array bounds (must not exceed 2).'. How so? as the value is 3

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Accepted Answer

Ameer Hamza
Ameer Hamza on 3 Dec 2020
Try this
x = myVal(:,1);
y = myVal(:,2);
z = myVal(:,3);
cmap = jet(256); %state colourmaop
min_val = min(z);
max_val = max(z);
colors = interp1(linspace(min_val, max_val, 256), cmap, z);
scatter(x, y, [], colors);

  3 Comments

Charlie Hillary
Charlie Hillary on 3 Dec 2020
Ok. I get an error for the z value, as this value is not supposed to exceed 2?
Charlie Hillary
Charlie Hillary on 3 Dec 2020
Note that my actually data file is much bigger than I stated. It works for this smaller data value though
Ameer Hamza
Ameer Hamza on 3 Dec 2020
Can you explain what do you mean by "I get an error for the z value, as this value is not supposed to exceed 2". What is the error message?

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More Answers (1)

Bjorn Gustavsson
Bjorn Gustavsson on 3 Dec 2020
Edited: Bjorn Gustavsson on 3 Dec 2020
To make it short and simple couldn't you just use scatter and let it automatically scale the values?
scatter(x,y,23,myVal,'filled')
colormap(jet(256))

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