what does y(:,1) means if y is a matrix ?

trig= -1*Y(:,1);
s= -1*Y(:,2);

Answer 1

[Mukhtar Ullah]

If you define a bidimensional array y, and you want to access all its elements on the first column: y(:,1) will do it. If you want to access to all the elements of the fift row: y(5,:) is the syntax you have to use. The colon means: take all the elements along the specified dimension. --Franco 18:36, 29 September 2006 (PDT)

Answer 2

[Stephen23]

 Y(:,1) % the first column of Y
 Y(:,2) % the second column of Y

This is basic MATLAB indexing:

http://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

http://www.mathworks.com/help/matlab/indexing.html

http://www.mathworks.com/help/matlab/getting-started-with-matlab.html