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# what correction is required in the code?

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Manav Divekar on 11 Nov 2021
Closed: Cris LaPierre on 11 Nov 2021
I am trying to perform 2*2 + 2*5 + 5*8, for [2 2 5 8] vector which is product of consicutive and sum of all. without using sum() & diff() and using for loop
function [out] = pairprodsum (m)
s = 0
for i = 1
b = m(1:end-1).*m(2:end);
s = s + b;
end
out = s;

James Tursa on 11 Nov 2021
If the homework assignment specifies you must use a loop, then I don't think the intent was for you to wrap a simple i=1 range around vectorized code. That being said, I suppose your "loop" technically qualifies.
b is a vector. You simply need to sum all the elements of b and return that. s = s + b does not sum the element of b ... it simply creates a new vector s that is a copy of b. You need different code to sum the elements of b. There are various ways to do this, which I will let you figure out.
James Tursa on 11 Nov 2021
How could you maybe change the for loop range so it added up all of the elements?

Jan on 11 Nov 2021
Edited: Jan on 11 Nov 2021
A hint: You want to perform this:
• s = 0
• s = s + 2*2
• s = s + 2*5
• s = s + 5*8
You need to loop over the indices of m. There is 1 iteration less than the number of elements of m.

R2021a

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