Error adding to a array

Question

I have used this method to add to arrays in other programs but this it doesn't seem to work. I am confused and can't find a answer to the problem.

Error:

The sample size is: Error using horzcat
CAT arguments dimensions are not consistent.

Error in CalculateElo (line 14) playerGroup = [playerGroup r];

Code:

function [accuracy] = CalculateElo (referenceElo , sampleSize, lower, upper)

fprintf('The sample size is: %d', sampleSize);

% Popoulate an new array
playerGroup = [];
playerGroup = [playerGroup referenceElo];

for i=1:(sampleSize - 1)
    %Create group size
    a = 0;
    b = 2000;
    r = (b-a).*rand(1000,1) + a;
    playerGroup = [playerGroup r];
end

rand(1000,1) is 1000 element row vecor. You cant add it to as a new column to playerGroup if it has different number of rows. — Marcin
– Marcin, Commented Feb 26, 2015 at 3:48

Dave Kielpinski · Accepted Answer · 2015-02-26 03:56:28Z

An expression like [x y] tries to concatenate the arrays x and y along dimension 2. Each row of an array in Matlab must have the same length (similarly, each column must have the same length). Hence, if size(x,1) = size(y,1), [x y] will return an array with size equal to size(x,1) along the first dimension and size(x,2)+size(y,2) along the second dimension. Otherwise you will get a cat error like the one you show.

r has size (1000,1), so unless the first dimension of referenceElo has size 1000, you will get a cat error.

You didn't mention the size of referenceElo, but I'm guessing it's a single number. You could use the ' (transpose) operator to write

playerGroup = [playerGroup r'];

returning an array of size (1,1001). Or you could use an expression of form [x;y], which concatenates along dimension 1:

playerGroup = [playerGroup;r];

returning an array of size (1001,1).

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