Specifying a sample of data from a table

I am trying to find how to specify a section of data to be analysed by a certain function. What is the method of doing so?

I'm currently using the circ_r and circ_std function kindly created by Philipp Berens available at http://www.jstatsoft.org/v31/i10, in order to analyse wind direction data.

Answer 1

[Dave B]

This sounds like a pretty broad topic, how to index things in MATLAB.

You might be interested in this documentation page about indexing: https://www.mathworks.com/help/matlab/math/array-indexing.html

Or maybe this article about indexing in MATLAB: https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

Here's some example code that calls circ_r with various subsets of an arbitrary theta

theta = [pi/3 pi/2 pi/5 2*pi];
circ_r(theta)             % all theta
circ_r(theta(1:3))        % first three theta
circ_r(theta([1 4]))      % first and fourth theta
circ_r(theta(end-1:end))  % last two theta
circ_r(theta(theta<pi/2)) % first and third theta
circ_r(theta(1:2:end));   % first and third theta

a = [1 2 3 4];
circ_r(theta(a>2))        % last two theta
circ_r(thata(a==1 | a>2)) % first, third, and fourth theta

If your data are in a table things are pretty similar:

t=table(theta',a');
circ_r(t.theta);
circ_r(t.theta(1:3));
circ_r(t.theta(t.a>2));
% etc