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From |
Jacob Wegelin <jacob.wegelin@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: extract rowname corresponding to row index of matrix |

Date |
Wed, 1 Apr 2009 18:57:55 -0400 |

Suppose we have a matrix BETA with -rownames- and -colnames-. Given the names of a row and of a column in BETA, it is possible to extract the indices of that row and of that column, as shown below. But is there an equally simple approach to the reverse problem? I mean: Given a row index, is there an elegant way to extract the name of that row? The solution below seems clumsy. As seen with -matrix LostRowNames-, extracting a one-row matrix from a one-column matrix causes the -rownames- to be lost. Thus my program uses a column join, which seems like a kludge. /* BEGIN STATA CODE */ clear all matrix input BETA=( 193\ 30 \ 133 \ 51\ 9.8 \ 0.1 ) matrix rownames BETA= dog cat rat mouse flea bubonic matrix colnames BETA=IQ mat lis BETA di "index of row called bubonic is " rownumb(matrix(BETA),"bubonic") di "index of column called IQ is " colnumb(matrix(BETA),"IQ") matrix LostRowNames=BETA[1,1] mat lis LostRowNames capture program drop getRowName program define getRowName, rclass local thismatrix="`1'" local rowindex=`2' matrix TWO= `thismatrix', `thismatrix' matrix TEMPORARY=TWO[`rowindex',1..2] local rowname: rownames TEMPORARY return local matrixname="`thismatrix'" return scalar rowindex=`rowindex' return local rowname = "`rowname'" end getRowName BETA 1 return list getRowName BETA 5 return list /* END STATA CODE */ Thanks for any insights Jacob A. Wegelin Assistant Professor Department of Biostatistics Virginia Commonwealth University 730 East Broad Street Room 3006 P. O. Box 980032 Richmond VA 23298-0032 U.S.A. E-mail: jwegelin@vcu.edu URL: http://www.people.vcu.edu/~jwegelin * * 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**:**RE: st: extract rowname corresponding to row index of matrix***From:*Roy Wada <roywada@hotmail.com>

**Re: st: extract rowname corresponding to row index of matrix***From:*Phil Schumm <pschumm@uchicago.edu>

**Re: st: extract rowname corresponding to row index of matrix***From:*Ben Jann <ben.jann@gmail.com>

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