how do i find argmax?
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how do i find argmax of, say x=[1 2] without any user defined function?
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Lukasz Laszko
2019-10-28
编辑：Lukasz Laszko
2019-10-28
4 个投票
I'm afraid the answer by Walter Roberson is not correct. According to docs the second returned value contains indices of the minimum/maximum values of x. So to find argmax, you need to call x(max_ind),
eg.
x=0.1:.01:4*pi;
[max_val max_ind]=max(cos(x))
argmax=x(max_ind)
-->> max_val=1
-->> argmax=2pi
-->> max_ind=619
3 个评论
Walter Roberson
2021-5-17
is Q1T a function? You have Q1T(0) which would not work if Q1T were a variable being indexed.
James Tursa
2021-5-17
编辑：James Tursa
2021-5-18
@Lukasz Laszko Argmax is defined as the elements of the domain (i.e., in this case the indexes) where the function (i.e., in this case the vector) obtains the maximum. See these definitions:
Walter's answer is correct according to these definitions.
Your use of cos(x) introduces another function inbetween that was not part of the original question. Did the original question have cos(x) that was subsequently edited out?
Walter Roberson
2021-5-18
In the case a function that is effectively f(x(K)) and what you wanted was the x(K) then it would not be unreasonable to take
fx = f(x);
[~, argidx] = max(fx);
argmax = x(argidx);
This adds an extra level of indirection, but it would be a common one.
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