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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

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

Subject |
st: RE: RE: sqrt of all elements of a matrix |

Date |
Thu, 17 Nov 2005 11:54:39 -0000 |

By the way, I'd agree with anyone who said that the syntax of -matewmf- was fairly horrible. If I were writing it today, I would have implemented a different syntax. But there's no point in a radical rewrite, given Mata. Nick n.j.cox@durham.ac.uk Nick Cox > Mata Answers This Admirably! > > . mata : > ------------------------------------------------- mata (type > end to exit) ------------------ > : m = (1,2,3\4,5,6\7,8,9) > > : sqrt(m) > 1 2 3 > +-------------------------------------------+ > 1 | 1 1.414213562 1.732050808 | > 2 | 2 2.236067977 2.449489743 | > 3 | 2.645751311 2.828427125 3 | > +-------------------------------------------+ > > Otherwise, in Stata <9, this is essentially the same question > as one asked a few days ago. An ancient program > to do this, and other _e_lement_w_ise _m_onadic > _f_unction problems, is -matewmf-: > > STB-56 dm79 . . . . . . . . . . . . . . . . . . Yet more > new matrix commands > (help matcorr, matewmf, matvsort, svmat2 if > installed) . . N. J. Cox > 7/00 pp.4--8; STB Reprints Vol 10, pp.17--23 > commands to produce a correlation matrix, elementwise monadic > function of another matrix, selected subsets of matrix rows > and columns, vec or vech of a matrix, elements sorted within > a vector, matrix from a vector, and commands to save matrices > > That name is so unlikely that you would never guess it, but > > . search matrix > > would have pointed to it. > > . matrix A = (1,2,3\4,5,6\7,8,9) > > . matewmf A B , function(sqrt) > > . mat li B > > B[3,3] > c1 c2 c3 > r1 1 1.4142136 1.7320508 > r2 2 2.236068 2.4494897 > r3 2.6457513 2.8284271 3 > > -matewmf- as published in STB-56 is about > 30 lines long, but can now be written much > more concisely: > > *! 1.1.0 NJC 17 November 2005 > *! 1.0.0 NJC 25 January 2000 > program matewmf > version 8.0 > gettoken A 0 : 0 > gettoken B 0 : 0, parse(" ,") > syntax , Function(str) > tempname C > mat `C' = `A' > forval i = 1/`=rowsof(matrix(`A'))' { > forval j = 1/`=colsof(matrix(`A'))' { > mat `C'[`i',`j'] = `function'(`A'[`i',`j']) > } > } > mat `B' = `C' /* allows overwriting of either `A' or `B' */ > end > > from which you can see, as would be expected, that > the problem boils down to a double loop. > > Nick > n.j.cox@durham.ac.uk > > I.A.C. van de Snepscheut > > > Is there a simple way to take the sqrt of all the elements in > > a matrix? * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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