MATLAB: Help understanding matlab code

concatenationfor loop

I am completely new to Matlab and I also don't have Matlab – but I have been asked to convert some Matlab code to another language, which is proving a little bit tricky for me. At the moment I am stuck with the following lines which are within a loop:
    d=s2(1)*ones(dim(1),1);
    for i=2:R,
        d=[d;s2(i)*ones(dim(i),1)];
s2 is a 1×2 matrix [0.1 1], dim = [3], and R is equal to 1 (the first time this code is evaluated)
My understanding is that the first line results in the 3×1 matrix
    0.1
    0.1
    0.1
But I am confused by what happens in the for loop a) since R is 1, is this a decrementing loop (evaluated with i=2 then i=1 ?) b) I really don't get the line d=[d;s2(i)*ones(dim(i),1)] at all
Could anyone help explain this to me ?

Best Answer

No. First of all dim(1) doesn't work - throws error. But I'll assume you copied it incorrectly and that it is a 3 by 1 column vector. What the code does is to tack on additional columns with different values that depend on s2's value. For example if s2(2) = 12.34 then the second column of d will be [12.34;12.34;12.34]. Then the third column of d will have elements with the value of s2(3), and so on. If R equals 1, then it doesn't even enter the loop at all so d stays the same as before the loop.
The loop does not decrement from 2 to R - it increments. To decrement, there would have to be a step of -1, like
for i = R : -1 : 2
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