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Jan
8
accepted Is the logarithm of sum of multiple variables with the constraint on sum of them Concave?
Jan
6
comment Is the logarithm of sum of multiple variables with the constraint on sum of them Concave?
@MichaelGrant yes. I edit the question title to make the question more formally. In fact in machine learning field saying Convex implies the meaning of being "Convex or Concave" BTW I am sorry if the title was not clear.
Jan
6
revised Is the logarithm of sum of multiple variables with the constraint on sum of them Concave?
added 15 characters in body; edited title
Jan
6
comment Is the logarithm of sum of multiple variables with the constraint on sum of them Concave?
the second derivative of log(1+x) is -1/((1+x)^2) which is always <0 for x>=0 and x<=1 and so it is concave. I think I missed the point on how this is not a concave function.
Jan
6
comment Is the logarithm of sum of multiple variables with the constraint on sum of them Concave?
Oh, I edit my question 25 minute ago and you answered it 22 minute ago. so you may didn't see the edit to the question:"constraint that ∑i=1:1:mαi=1∑i=1:1:mαi=1 and they are positive". I am really sorry
Jan
6
comment Is the logarithm of sum of multiple variables with the constraint on sum of them Concave?
thanks Giuseppe, But I didn't catch your idea exactly. we know that x>=0 and x<=1. so you say that log(x+1) is not convex for 0<=x<=1?
Jan
6
revised Is the logarithm of sum of multiple variables with the constraint on sum of them Concave?
added 22 characters in body
Jan
6
asked Is the logarithm of sum of multiple variables with the constraint on sum of them Concave?
Jan
5
comment is this function an ill-shape convex function?
thanks for your reply. i edit the question to be more obvious(it has a little typo also). also yes, all things except the alphas are simple constants
Jan
5
revised is this function an ill-shape convex function?
deleted 49 characters in body
Jan
5
revised is this function an ill-shape convex function?
deleted 49 characters in body
Jan
5
revised is this function an ill-shape convex function?
added 5 characters in body
Jan
4
revised is this function an ill-shape convex function?
added 60 characters in body
Jan
4
comment is this function an ill-shape convex function?
I have deleted the old question because I think that this question(new one) makes sense better
Jan
4
asked is this function an ill-shape convex function?
Oct
21
asked Is the output of a genral deterministic system to an Stationary input, Stationary?
Oct
15
asked Is there any real world phenomena that can be modeled approximately as Strict Sense Stationary process?
Sep
17
awarded  Promoter
Sep
14
comment right way of weighting sampling for a distribution?
yes, Thank you a lot.@joriki
Sep
14
comment right way of weighting sampling for a distribution?
I think there was an answer here which is deleted now. unfortunately I didn't read it.