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I want to calculate a sum of products of the form :

1.1*a^2*b^9+1.4*a^7*b^4+0.25*a^6*b^8

where a and b are constants.

This expression is the sum of 3 products, I am giving it just for simplification, but the reality is that I have to calculate a sum of 47 products of this form and in each product the coefficients (1.1, 1.4, 0.25) are different and the powers (2, 9, 7, 4, 6, 8) are also different from one product to the other.

So, my question is : Is there any notation that I can use to calculate the sum above without having to repeat each time the constants a and b ??

Azzi Abdelmalek
on 8 Oct 2012

Edited: Azzi Abdelmalek
on 8 Oct 2012

example

x=11

a=[1 2 3 4];

p=[10 15 20 25]

sum(a.*x.^p)

% the result is

a(1)*x^p(1)+a(2)*x^p(2)+...

./ and .* and .^ are operations element by element

for your case

c=[1.1 1.4 0.25 ]

p1=[2 7 6]

p2=[9 4 8]

a=10;b=30

out=sum(c.*a.^p1.*b.^p2)

you can also create a function

f1=@(c,p1,p2,a,b) sum(c.*a.^p1.*b.^p2)

then

out=f1(c,p1,p2,a,b)

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kamal kiki
on 8 Oct 2012

Azzi Abdelmalek
on 8 Oct 2012

Kamal it's not a function file. just write

f1=@(c,p1,p2,a,b) sum(c.*a.^p1.*b.^p2)

then

c=[1.1 1.4 0.25 ]

p1=[2 7 6]

p2=[9 4 8]

a=10;b=30

out=f1(c,p1,p2,a,b)

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Wayne King
on 8 Oct 2012

Why are you entering it like that?

mytotal = @(c,p1,p2,a,b)sum(c.*a.^p1.*b.^p2)

mytotal([1.1 1.4 0.25 ],[2 7 6],[9 4 8],10,30)

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