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Plot 2D-histogram for X and Y

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BN
BN on 20 Jul 2020
Commented: Star Strider on 29 Jul 2020
Dear all,
I have two types of data sets (X and Y) with equal size, which I would like to plot 2D-histogram of them, in order to compare X by Y.
So the larger the scatter implies the greater
disagreement.
I used this script below:
data = [X,Y];
hist3(data,'CdataMode','auto')
xlabel('observed')
ylabel('modeled')
colorbar
view(2)
And here is my achievement:
Unfortunately, as you can see this plot does not represent my goal, for instance, please look at this figure below (I want to achieve a plot like this below):
So any suggestion is really helpful.
Thank you all
  3 Comments
Roger J
Roger J on 20 Jul 2020
Try:
>> hist(X)
>> hist(Y)
I did, and it plotted each vector, and most(almost all) of your data is less than 50 for both X and Y. Seems like the histogram is correct for that data.

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Accepted Answer

Star Strider
Star Strider on 20 Jul 2020
Try this:
D1 = load('X.mat');
D2 = load('Y.mat');
X = D1.X;
Y = D2.Y;
data = [X,Y];
hh3 = hist3(data, 'Nbins',[1 1]*60);
figure
image(flipud(hh3))
ax = gca;
xt = ax.XTick;
yt = ax.YTick;
ax.XTickLabel = xt*10;
set(ax, 'YTick',[0 yt], 'YTickLabel', [flip([0 yt])]*10)
producing:
Experiment to get different results.
.
  2 Comments
Star Strider
Star Strider on 29 Jul 2020
As always, my pleasure!

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More Answers (3)

Cris LaPierre
Cris LaPierre on 20 Jul 2020
Edited: Cris LaPierre on 20 Jul 2020
A couple issues to be aware of.
  1. You are using a different colormap. It looks like the goal image is using Jet.
  2. Your X and Y values are dominated by the counts in the first bin (histograms below). Consider using caxis to keep the colorbar focused on the desired range.
Try adding (and adjusting to meet your needs) the following code.
colormap("jet")
caxis([0,80])
  1 Comment
BN
BN on 29 Jul 2020
Thank you so much +1

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Image Analyst
Image Analyst on 20 Jul 2020
Your data does not peak in the 100 to 250 range. It peaks around 0:
load('x.mat');
load('y.mat');
data = [X,Y];
h = histogram2(X, Y,100)
xlabel('observed')
ylabel('modeled')
% Set colormap, but it won't have any effect.
colormap(jet(256));
colorbar;
% view(2)
% Zoom in on the 0-200 range.
xlim([0,200]);
ylim([0,200]);
% Label the plot.
title('Counts', 'FontSize', 20);
xlabel('X', 'FontSize', 20);
ylabel('Y', 'FontSize', 20);
coefficients = polyfit(X, Y, 1);
xFit = xlim;
yFit = polyval(coefficients, xFit);
hold on;
plot3(xFit, yFit, [0,0], 'r-', 'LineWidth', 3);
c = corrcoef(X, Y)
This is essentially just what you saw, just that I used narrower bins and used a more modern function: histogram2(). Why do you think it's wrong and that you should have more counts in the 100-250 range?
  1 Comment
BN
BN on 29 Jul 2020
Yes you right, Thank you so much. +1

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Steven Lord
Steven Lord on 20 Jul 2020
In addition to histogram2 which Image Analyst suggested, take a look at the heatmap function. I think showing a heatmap of the data binned by histogram2 or histcounts2 will be pretty close to the picture you want.
  1 Comment
BN
BN on 29 Jul 2020
Yest Thank you so much +1

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