Need help in uderstanding this piece of code

Hello All, This is the code I found somewhere in a script :

output(idx,:) = [y1(ii),z,smax];

Can anyone explain me the logic here? I mean what's expected out of this code?

[Stephen23]

These are all very basic MATLAB operations: indexing, concatenation, and assigning to variables. You should do the introductory tutorials, which introduce these basic MATLAB operations:

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

Answer 1

[Adam]

idx defines the row of the 'output' matrix being written to and ':' says to just fill as many columns in that row as there are outputs from the right-hand side of the equation.

The stuff on the right is just an array of variables, the first being indexed into by some other variable so I assume in this case there are 3 elements in that vector and these will fill the 3 columns for row idx in 'output'.

[Walter Roberson]

In the code it is not strictly necessary that z or smax be scalars; they could be vectors, as long as the total length of the three variables matched the number of columns in the output array.

Answer 2

[Thorsten]

You generate a row vector

[y1(ii),z,smax]

And this vector is assigned to row "idx" of the output matrix

output(idx,:) = [y1(ii),z,smax];

You cannot do

output(idx) = [y1(ii),z,smax];

because you cannot assign a 1xN vector to a single number output(idx). So you need the ,: to assign the vector to a row.