Multiple specific elements in an array

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rockstar49
rockstar49 2020-2-20
评论： rockstar49 2020-2-20
I have a matrix [a b c d e f g]. I want to sum [2*(a + b) + 3*(c+d) +4*(e+f)]. How do i go about doing this ?

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Bhaskar R
Bhaskar R 2020-2-20
Assuming a, b,c, d, ..g are values in the vector say X
X = 1:7;
sum([2:4].*[sum(reshape(x(1:6), 2,3))]);
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Bhaskar R
Bhaskar R 2020-2-20
No, I mean to say that you have asked for "sum [2*(a + b) + 3*(c+d) +4*(e+f)]" then asking for "Now i want to sum 2*.36 + 3*(.14 + .13 +.12 +.1 +.09) +4*(.04 +.02)". Each time we can't change the evaluation of the statement. If there are only less than 10 entries you can write complete statement without using any commands using matlab indexing.
for this
sum 2*.36 + 3*(.14 + .13 +.12 +.1 +.09) +4*(.04 +.02) =
res = sum([2*x(1), 3*x(2:6), 4*x(7:8)]);
For information on indexing https://in.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html
I think i am clear!
rockstar49
rockstar49 2020-2-20
thank you! I did not know of this.
Best,
Zakir M

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