copy 1st element of an array to 20 first indexes of second array in matlab

You can do this using simple indexing in Matlab. Here's how:

main.m
array2(1:20) = array1(1);
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This will copy the first element of array1 into the first 20 elements of array2.

Note that if array2 is not already initialized, you will need to create it first:

main.m
array1 = [1 2 3 4 5];  % Example arrays
array2 = zeros(1, 20); % Initialize array2 with 20 elements, all set to 0

array2(1:20) = array1(1);
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This will copy the value 1 from array1(1) into the first 20 elements of array2, resulting in array2 being:

main.m
array2 = [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1];
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