How do I plot intensity of points on a scatter plot?

Hey all, I'm a beginner at this but would appreciate some help!

I have a plot of x and y coordinates and I would like to plot them to show the intensity of the points. For example if an (x,y) point occurs quite a bit then it will be dark red on the plot whereas a point that only occurs once will be light blue or something similar. I would greatly appreciate if anyone could help get me started as I haven't been able to find anything or figure it out on my own.

Answer 1

[dpb]

Nuthin' to it...try

x=randn(100,1);y=randn(100,1);  % sample data
scatter(x,y,20*abs(y),y,'filled')
colormap(hsv)

See

doc scatter % for details

ADDENDUM

Oh, I just happened to reread the question; I scanned it too quickly before, it seems--the above is color/size proportional to magnitude, not frequency.

[~,bin]=histc(y,linspace(min(y),max(y),10));  % location of nth bin 
scatter(x,y,20*abs(y),bin,'filled')

Above is size of marker by magnitude, color by frequency of occurrence...as always, "salt to suit"...

[Olivia Licata]

Every time I run these two lines, ([~,bin]...) no figures result. Even after deleting the lines of code, MATLAB stops running scripts and I have to restart my whole system.

[dpb]

Show exactly what code these two lines are...just checked here to make sure were no typos, etc.

Answer 2

[Thorsten]

If the x and y values are not 100% identical, you have to set up a grid and count the number of points in each grid, using hist2

x=randn(10000,1);y=randn(10000,1);  % sample data
% adapt these values according to your data
Nbins = 64; 
xmin = -4; xmax = 4;
ymin = -4; ymax = 4; 
H = hist3([x y], {linspace(xmin, xmax, Nbins), linspace(ymin, ymax, Nbins)});
imshow(H, [])
colormap jet