How to plot these function plesa help
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Hello.
I tried almost everything, but with no succsess. Maybe anyone knows and can share matlab code to plot these function: f(x) = (4 - 2.1*x1^2 + x1^4/3)*x1^2 + x1*x2 + (-4 + 4*x2^2)*x2^2
the function is taken from here: http://www.mathworks.com/help/gads/examples/minimization-using-simulated-annealing-algorithm.html
Thank you
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Mischa Kim
2015-6-17
Joe, you could use
[x1,x2] = meshgrid(0:0.5:10,0:0.5:10);
f = (4 - 2.1*x1.^2 + x1.^4/3).*x1.^2 + x1.*x2 + (-4 + 4*x2.^2).*x2.^2;
surf(x1,x2,f)
5 个评论
Joe Gani
2015-6-17
Mischa Kim
2015-6-17
It is a slightly different function (see 4/3) and a different range. Try
[x1,x2] = meshgrid(0.9:0.1:1.4,-1:0.1:1);
f = (4 - 2.1*x1.^2 + x1.^(4/3)).*x1.^2 + x1.*x2 + (-4 + 4*x2.^2).*x2.^2;
surf(x1,x2,f)
Joe Gani
2015-6-17
Walter Roberson
2015-6-17
The function has x1^(4/3) . When x1 is negative, the result is complex.
Note that x1^(4/3) is not the same thing as (x1^4)^(1/3) and is potentially different again from (x1^(1/3))^4; just as x1^(1/2) is not the same as (x1^2)^(1/4) . Taking a number to a fractional power requires choosing one root, not hunting through the integer multiples of the exponent to find one that will make the root real-valued.
Perhaps you want,
f = (4 - 2.1*x1.^2 + (x1.^4).^(1/3)).*x1.^2 + x1.*x2 + (-4 + 4*x2.^2).*x2.^2;
but be aware that might not match the formula on the paper.
Joe Gani
2015-6-17
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