element wise sum in array

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Majbah
Majbah 2014-3-28
回答： dpb 2014-3-28
Hello,
I have a formula to calculate value, but, the value of elements will come from some elements of array. Like:
s_k=0.6 * t * x^3 * c^-4
t = [20 30 22 32 10 15 12 14 15 20];
x = [45 34 15 30 22 25 17 20 14 25];
c= [10 10 10 10 10 10 10 10 10 10];
p=[1 3 5 7];
I need the value of sum(s_k(p)).
How can I get that?
Thanks in advance.

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采纳的回答

Marta Salas
Marta Salas 2014-3-28
编辑：Marta Salas 2014-3-28
You have to use a dot in front of the operation: .* .^ to mean element-wise operation in matlab
t = [20 30 22 32 10 15 12 14 15 20];
x = [45 34 15 30 22 25 17 20 14 25];
c= [10 10 10 10 10 10 10 10 10 10];
s_k=0.6 * t .* x.^3 .* c.^-4
p=[1 3 5 7];
sum(s_k(p));

更多回答（1 个）

dpb
dpb 2014-3-28
Good spot for function handle...
>> f=@(t,x,c) 0.6.*t.*x.^3./c.^4
f =
@(t,x,c)0.6.*t.*x.^3./c.^4
>> f(t(p),x(p),c(p))
ans =
109.3500 4.4550 6.3888 3.5374
>> sum(f(t(p),x(p),c(p)))
ans =
123.7312
>>

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