how to find the sum of product of elements of an array in matlab

Question

Chandradhar Savanth 2013-10-3

评论： Biruk Tadesse 2020-12-31

hi,

let p = [1 2 33 44 -11 -22] is single row multiple column matrix

i = index of elements of 'p',

in this case i = [1 2 3 4 5 6]

then x = sum(i*p(i)),i.e,'x' is equal to sum of product of corresponding elements of 'i' and 'p';

how to get 'x',

i know that we can compute 'x' by using loops.but is there any better way other than loops.

Answer 1

Azzi Abdelmalek 2013-10-3

p = [1 2 33 44 -11 -22]
i = [1 2 3 4 5 6]
out=sum(i.*p(i))

Its working

thank you Azzi Abdelmalek ,

in the same above question can i find sum of product of only first 4 elements.

i.e,x = sum(i.*p(i)),where 'i' and 'p' takes first four elements of there respective arrays.

Regards,

Chandradhar Savanth.

Azzi Abdelmalek 2013-10-3

out=sum(i(1:4).*p(i(1:4)))

Answer 2

编辑：Debnarayan Bhattacharya 2019-10-1

Easier way is:

p = [1 2 33 44 -11 -22]
i = 1:size(p, 2)
out = p * i'

Alternately,

out = dot(p, i)

I am not aware of a function named sumproduct in MATLAB. However, the dot() serves the purpose.

Biruk Tadesse 2020-12-31

any one help me p/se matlab cod for the equation