vector3d random sample

Hi all,

I have a problem plotting some data. There are too many points and therefore I want to plot a random sample.

The class is vector3d and contains 13717 points. I would be interested in plotting around a 1000 points or just a certain percentage. However, I keep getting the following error:

'Error using reshape

Product of known dimensions, 3, not divisible into total number of elements, 13717.'

Hope anyone here can help me.

Cheers,

Rick

Answer 1

[KSSV]

n = 13717 ; % totalpoints 
m = 1000 ;  % points to select 
x = rand(n,1) ; y = rand(n,1) ;  % random data for demo  
idx = randperm(n,m) ;  % select m points outof n randomly 
plot(x(idx),y(idx),'*r') % plot the points selected

[Rick Verberne]

Thank you for your help. It didn't work for me but I have found a workaround.

[KSSV]

Why it din't work? It selects m random points out of n. What did work for you?

[Rick Verberne]

I think because of the structure of that class, or maybe I just did something wrong. The toolbox allows for sampling when you first load your data. So I created a second dataset. I can use the more detailed information for creating images and calculations on boundaries and use the reduced set for some plots where plotting everything just convolutes the data.

Answer 2

[Ameer Hamza]

vector3d is not a MATLAB class. In case you have data points in the form of n*3 matrix. You can do something like this

M = rand(13717, 3); % for example
idx = randperm(size(M,1), 1000); % select 1000 points from 13717
M_small = M(idx, :); % 1000x3 matrix

[Rick Verberne]

Ah okay, this is the description in the Workspace but it was created via a different programma written for matlab

[Ameer Hamza]

So do you have a custom class vector3d?

[Rick Verberne]

Yes, or at least the person who wrote it. It is a program called MTEX

https://mtex-toolbox.github.io/vector3d.vector3d.html