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From |
"Abhimanyu Arora" <abhimanyu.arora@student.kuleuven.be> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: query regarding mata |

Date |
Sun, 11 Apr 2010 06:50:11 +0200 |

Dear statalist users I am trying to use mata to find the fixed point of a contraction mapping. Basically I have 5 non-linear equations in 5 variables (all explicitly expressed in terms of the others). Since I wasn't successful with 'optimize', I tried to use the following idea-start with a vector of zeros and put the elements of vector of unknowns into the RHS of the equations till convergence is achieved (updated value 'almost equal' to previous one). Following is my code and output: clear mata . mata ------------------------------------------------- mata (type end to exit) ---------------------------------------------------------------------------- -------------------------- : : real vector fpt(real scalar x,real scalar y) \\x and y are the parameters of the equations > { > v=0,0,0,0,0 > > while (mreldif(v,lastv)<10^(-6)) { > > > lastv=v > > v[1,1]=0.5775+ln(exp(x+0.9*v[1,2])+exp(y+0.9*v[1,1])) > v[1,2]=0.5775+ln(exp(2*x+0.9*v[1,3])+exp(y+0.9*v[1,1])) > v[1,3]=0.5775+ln(exp(3*x+0.9*v[1,4])+exp(y+0.9*v[1,1])) > v[1,4]=0.5775+ln(exp(4*x+0.9*v[1,5])+exp(y+0.9*v[1,1])) > v[1,5]=0.5775+ln(exp(5*x+0.9*v[1,5])+exp(y+0.9*v[1,1])) > > > } > return(lastv) > } note: variable lastv may be used before set : : : fpt(2,3) mreldif(): 3200 conformability error fpt(): - function returned error <istmt>: - function returned error r(3200); : : : end ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- ------------------------ The error code indicates that there is some operation that is not compatible with the matrices involved. It would be nice if you could point out the mistake. Thank you very much Abhimanyu Arora PhD student KU Leuven * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**st: RE: query regarding mata***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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