vector3d random sample

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Rick Verberne
Rick Verberne on 18 Jun 2020
Commented: Rick Verberne on 19 Jun 2020
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

Answers (2)

KSSV
KSSV on 18 Jun 2020
Edited: KSSV on 18 Jun 2020
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
  3 Comments
KSSV
KSSV on 18 Jun 2020
Why it din't work? It selects m random points out of n. What did work for you?
Rick Verberne
Rick Verberne on 19 Jun 2020
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.

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Ameer Hamza
Ameer Hamza on 18 Jun 2020
Edited: Ameer Hamza on 18 Jun 2020
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
  3 Comments
Ameer Hamza
Ameer Hamza on 18 Jun 2020
So do you have a custom class vector3d?
Rick Verberne
Rick Verberne on 19 Jun 2020
Yes, or at least the person who wrote it. It is a program called MTEX

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