How do I update array elements through a loop?

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Justin Saxon
Justin Saxon 2021-11-9
回答： Steven Lord 2021-11-9
How do I update an element in array. So I have an array of say 5 zeros:
[00000]
How do I change certain elements of the array one at a time.
What I mean is how do I go from the following:
[0 0 0 0 0 0]
[4 0 0 0 0 0]
[4 1 0 0 0 0]
[4 1 9 0 0 0]
[4 1 9 6 0 0]
[4 1 9 6 2 0]
[4 1 9 6 2 8]
  2 个评论
Sargondjani
Sargondjani 2021-11-9
It is not so clear what you exactly want to do. But maybe this helps?
cross_corr = zeros(1,1999)
%Compute each element:
for ii = 1:size(cross_corr,2)
cross_corr(1,ii) = %your computation comes here
end
Justin Saxon
Justin Saxon 2021-11-9
编辑：Justin Saxon 2021-11-9
Sorry, I included way too much pointless information in the question.
How do I have an array of 5 zeros -----> [0 0 0 0 0]
and update the elements of the arrays one at a time.
So I go through a loop and end up with a variable. I want to plug that variable into element 1 of the array. Then the loop goes back through and the variable is something new and the new variable goes in element 2. This goes on 1999 times. I have the code I just don't know how to replace the zero with my variable. Its something very simple

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回答（1 个）

Steven Lord
Steven Lord 2021-11-9
Ran in:
The empty Static method (you'd made a typo and used emtpy instead of empty) creates a 0-by-0 array of the class when called with no input arguments. When called with a size vector or multiple arguments it creates an array of that size (and at least one of the dimensions must be 0.)
Instead of creating a 0-by-0 empty and assigning to elements of it (growing it each time) I'd preallocate the matrix of the appropriate (non-empty) size and then assign to it. The zeros function will let you do this preallocation with each element of the result containing 0.
z = zeros(1, 5)
z = 1×5
0 0 0 0 0
z(3) = 42
z = 1×5
0 0 42 0 0
z(2) = -999
z = 1×5
0 -999 42 0 0
z(5) = NaN
z = 1×5
0 -999 42 0 NaN

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