Visualizing density of points?

I have a matrix A with dimension of 288*15581 where 288 is the length of time. Hence, I have 15581 curves. when I plot them I have the picture attached.

The problem is I do not know how many point have been gathered at one specific location. Having A, how can I see the density of points? I think heat map can do it but I have no idea.

Answer 1

[jonas]

You can probably use hist3. See some similar questions here:

https://se.mathworks.com/matlabcentral/answers/415851-how-to-make-a-heatmap-with-density-of-points

https://se.mathworks.com/matlabcentral/answers/409660-can-i-use-contourf-with-two-matrices

Upload some data if you need code.

[Seyyed Mohammad Saeed Damadi]

The matrix A is data for 500 curves with length 288. The scatter plot is as follows:

Could you tell me how to use hist3 and and heat map?

[jonas]

Here are some examples with different bin types. The first one shows the distribution of points over the area, the second one shows the same but with more bins and the third one shows the number of points in different intervals of y.

% Load data
data=load('A.mat');
y=data.A;
x=repmat(1:288,500,1)';

% Plot with standard settings
subplot(1,3,1)
hist3([x(:),y(:)],'CDataMode','auto')
axis tight

% n pts in intervals of y
subplot(1,3,2)
biny=75;
binx=75;
hist3([x(:),y(:)],[binx biny],'CDataMode','auto')
axis tight

% n pts in intervals of x
subplot(1,3,3)
biny=20;
binx=1;
hist3([x(:),y(:)],[binx biny],'CDataMode','auto')
axis tight

[Seyyed Mohammad Saeed Damadi]

Could you tell me how to remove grid on the figure?

Also, I used colormap(gray) and the result is:

I want it in the reverse, I mean white background and black spots. Could you please help me?

[jonas]

Im on phone so cannot try it out myself, but add

hist3(... 'edgecolor', 'none')

to your hist function. You can also try 'interp' instead of 'none'. Second question, try

colormap(flipud(gray))

You could also check out thus link for how to combine hist3 with pcolor

https://se.mathworks.com/help/stats/hist3.html#brx09qw-1157

[Seyyed Mohammad Saeed Damadi]

It worked. Thanks.

Answer 2

[KSSV]

Read about pcolor, surf.

[Seyyed Mohammad Saeed Damadi]

That does not help.

[KSSV]

At a given time..you want to see how many points have certain y value?

[Seyyed Mohammad Saeed Damadi]

Not exactly. I need to know how many points are in a certain small interval of y from zero to one. Then I will be able to count them and compare them with other y's in certain time. The more points, the more color in y-axis. I know how to think of it but I do not know how to implement it. Please do not refer me to a document. To help me, suppose you have a given matrix A including 50 sinusoidal with different frequency sampled at 200 points. How can you show more density of figures between -1 and 1?