# How to add every nth element of an array to the nth+1 element?

16 views (last 30 days)
Niklas Kurz on 4 Jun 2024
Commented: Voss on 4 Jun 2024
I wonder if there is a short expression for the task above. For example if I had an array like this
a = [1, 2, 3, 3, 4, 5, 5, 6, 7, 7, 8, 9]
How can I add, let's say every 3rd element to every 4th element to get an array like this ?
a = [1, 2, 3+3, 4, 5+5, 6, 7+7, 8, 9]
I can do this with some ugle lines of code, but what if you got a more elegant way?

Voss on 4 Jun 2024
a = [1, 2, 3, 3, 4, 5, 5, 6, 7, 7, 8, 9];
a(3:3:end-1) = a(3:3:end-1)+a(4:3:end);
a(4:3:end) = []
a = 1x9
1 2 6 4 10 6 14 8 9
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Niklas Kurz on 4 Jun 2024
Allright thanks. I'll just create a function to make it cleaner and hide the operations.
Voss on 4 Jun 2024
Sounds good!

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