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Mephist
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Posts: 1
Joined: January 3rd, 2011, 2:16 am

Portfolio optimization with factor tilting while constraining volatility

June 13th, 2017, 3:32 am

Hi, what optimizer I can use (preferably in R) to solve the following portfolio optimization problem:

min(fTx)
   st:  
1.  -a <= SUM x(i) <= b
2. -c <= x(i) <= d
3.  e <= SUM |x(i)| <= f
4. SQRT (xT COV x) <= g

a,b,c,d,e,f,g - positive. f is a vector. x - weights. COV var-covar matrix estimated from historical data. The problem without constrain 4 can be solved with linear solver ( with some tricks for condition 3). Condition 4 makes constrain non-linear, but quadratic. Any suggestion would be helpful. Thanks. 
 
 
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Cuchulainn
Posts: 22926
Joined: July 16th, 2004, 7:38 am

Re: Portfolio optimization with factor tilting while constraining volatility

June 28th, 2017, 11:48 am

Lagrange multiplier, barrier, penalty.

https://en.wikipedia.org/wiki/Lagrange_multiplier
 
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ExSan
Posts: 495
Joined: April 12th, 2003, 10:40 am

Re: Portfolio optimization with factor tilting while constraining volatility

June 28th, 2017, 10:59 pm

Lagrange multiplier, barrier, penalty.
https://en.wikipedia.org/wiki/Lagrange_multiplier
exactly! That is what I thought, though Mephist provides poor  information about his aims
 
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Cuchulainn
Posts: 22926
Joined: July 16th, 2004, 7:38 am

Re: Portfolio optimization with factor tilting while constraining volatility

June 29th, 2017, 10:19 am

A quick "constrained optimisation in R" throws up

https://cran.r-project.org/web/packages ... nloptr.pdf

etc.