# How do I put arrays into a for loop

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studentmatlaber on 31 Mar 2021
Commented: Image Analyst on 31 Mar 2021
I have 24 arrays (such as y1, y2, y3 ...). I want to calculate the average of each of the N elements of these arrays. For example, first the average of the first N elements of the y1 array will be calculated. After calculating the average of the first N elements of 24 arrays, I want it to be saved in an array.
I wrote the following code for this, but I can only calculate for a array.
N = 5;
sub = 0;
for i = 1: 1: N
sub = sub + y1 (i);
end
mean = sub / N;
Stephen23 on 31 Mar 2021
"I have 24 arrays (such as y1, y2, y3 ...)."
How did you get all of those arrays into the workspace? Did you write them all out by hand?
"I want to calculate the average of each of the N elements of these arrays."
That would be a trivially easy task if you designed your data better (i.e. used one array and indexing).

Jan on 31 Mar 2021
Edited: Jan on 31 Mar 2021
Hiding an index in the name of a set of variables is the main problem here. This makes it hard to access the variables. Use an index instead:
Data = {y1, y2, y3, y4}; % et.c...
% Much better: Do not create y1, y2, ... at all, but the array directly
MeanData = zeros(1, numel(Data));
for k = 1:numel(Data)
MeanData{k} = mean(Data{k});
end
If there is any reason not to use the mean() function:
MeanData = zeros(1, numel(Data));
for k = 1:numel(Data)
MeanData{k} = sum(Data{k}) / numel(Data{k});
end
Image Analyst on 31 Mar 2021
To get the mean of only the first N elements
for k = 1:numel(Data)
thisArray = Data{k};
MeanData(k) = mean(thisArray(1 : N));
end

VBBV on 31 Mar 2021
Ok. Use a different variable name for mean It is a standard function in matlab. See if it then works