Create a vector with for loop with mathematical operations

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Hasan Berke Bankoglu 2020-5-10

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https://ww2.mathworks.cn/matlabcentral/answers/524411-create-a-vector-with-for-loop-with-mathematical-operations

评论： Stephen23 2022-1-23

采纳的回答： KSSV

w=[5 4 3 2]

Use this vector in a mathematical expression to create the following vectors:

My code snippet is below, code for that question. When I run it, I can't get expected result. I just want to create a vector as noted above.How can I solve that question?

w=[5 4 3 2]

for i= w

a3=[1/(i+i)]

b3 =[i^i]

c3 =[i/sqrt(i)]

d3 =[(i^2)/(i^i)]

end

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KSSV 2020-5-10

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Read about ., element by element operations.

w = [5 4 3 2] ;
a = 1./(w+w) ;
b = w.^w ; 
c = w./sqrt(w) ; 
d = w.^2./w.^w ; 

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Hasan Berke Bankoglu 2020-5-10

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Toder 2020-5-10

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To fix your current code, you need to use indices in the for loop.

w=[5 4 3 2]
for i = w
    a3(6-i)=[1/(i+i)]
    b3(6-i) =[i^i]
    c3(6-i) =[i/sqrt(i)]
    d3(6-i) =[(i^2)/(i^i)]
end

This assigns a3(1) in the first loop, a3(2) in the second, etc. Your code reassigns the scalar a3 each loop. The indices I use are somewhat strange because we're looping over w, which is fine, it just makes indices harder to keep track of. You could do it differently by using a counter:

w=[5 4 3 2]
j = 1
for i = w
    a3(j)=[1/(i+i)]
    b3(j) =[i^i]
    c3(j) =[i/sqrt(i)]
    d3(j) =[(i^2)/(i^i)]
    j = j+1
end

Or you could have your for loop count from 1 to 4:

w=[5 4 3 2]
for i = 1:4
    a3(i)=[1/(w(i)+w(i))]
    b3(i) =[w(i)^w(i)]
    c3(i) =[w(i)/sqrt(w(i))]
    d3(i) =[(w(i)^2)/(w(i)^w(i))]
end

All this being said, I recommend "vectorizing" your code where possible. Dot operators perform arithmetic element-by-element, see the documentation for dot multiplication here. For instance, the whole a3 vector can be defined this way:

a3 = 1./(2*w)