Making a loop with 3 variables

2017 7 29
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更新时间：2020 1 31
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Hello,
I'm new to matlab and need help making a code for obtaining an optimize value. Lets say I have y=a^2-8*b+C*2/ab for example and I have to obtain y<x where a=1:5, b=30:100 and c=20:30.
So I first use an initial value for a, b, and c, then if y<x is not met it will recalculate with a different value a,b,c until y<x is satisfied. Basically making a loop.
Is it possible to code this?
Thanks in advance

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Ahmed raafat
Ahmed raafat 2017-7-29

2 个投票

why loop??? use this beautiful method
a=1:5;
b=30:100;
c=20:30;
[a,b,c]=meshgrid(a,b,c);
y=a.^2+8*b+2.*c./a./b;
This will produce matrix with size(71,5,11)
you can get the minimum result in the next line
x=min(min(min(y)));

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Ahmed raafat
Ahmed raafat 2017-7-29
编辑：Ahmed raafat 2017-7-29
if you want all values of y<x
[r1,r2,r3]=find(y<x);
Walter Roberson
Walter Roberson 2017-7-29
Close, but to get the proper indices you should use
idx = find(y<x);
[r1, r2, r3] = ind2sub(size(y), idx);
The reason for this is that when you use three outputs to find(), the third output is the value at the location, which is especially useful for sparse arrays.
JohnB
JohnB 2020-1-31
Hi, and where can you get the values of a_min, b_min and c_min to obtain the minimum ?
Regards

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