Summation of an array

How can i code this in matlab?

Answer 1

[JESUS DAVID ARIZA ROYETH]

if length(P) and length(Y) is N:

x=sum(P.*Y)

in another case:

N=5; %set any value for N
x=sum(P(1:N).*Y(1:N))

[Barry Allen]

What if N is different?