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

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: subsetting a matrix by rowname and column name |

Date |
Tue, 24 Mar 2009 14:24:54 -0400 |

Thanks to Austin Nichols for this insight. But a slight modification of the code seems to reveal the following: Although a variable and a scalar can both have the same name (for example, -b- in Austin Nichols's exammple), it appears that a matrix and a scalar cannot have the same name. Is this correct? See what happens below when I try to -matrix list- b after scalar b has been defined. sysuse auto, clear g b=1 qui probit foreign mpg mat b=e(b) mat lis b scalar b=el(matrix(b),1,colnumb(matrix(b),"mpg")) di scalar(b) mat lis b /* generates an error */ di b Am I missing something? Jake On Sat, Mar 21, 2009 at 6:09 PM, Austin Nichols <austinnichols@gmail.com> wrote: > Jacob Wegelin <jacob.wegelin@gmail.com> : > Try: > > sysuse auto, clear > g b=1 > qui probit foreign mpg > mat b=e(b) > scalar b=el(matrix(b),1,colnumb(matrix(b),"mpg")) > di scalar(b) > di b > > Note that matrices, scalars, and variables share the same namespace, > which often leads to cryptic error messages or huge mistakes for the > less careful (you may prefer to use a local instead to avoid this > problem). So say matrix(b) instead of b, and scalar(p) instead of p. > > On Sat, Mar 21, 2009 at 5:43 PM, Jacob Wegelin <jacob.wegelin@gmail.com> wrote: >> The results below indicate that >> >> (1) One can extract a cell from a matrix using the row and column names, but >> >> (2) the value returned cannot be assigned to a scalar, only to a >> one-by-one matrix. (See error below.) >> >> (3) By contrast, when one extracts a cell from a matrix using row and >> column *indices*, the value can be assigned to a scalar. >> >> Is there some good reason for this? I'd ideally like to extract a >> scalar by row and column name, since this would be less error-prone. >> >> Thanks for any insights > * > * 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/ > * * 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/

**References**:**st: subsetting a matrix by rowname and column name***From:*Jacob Wegelin <jacob.wegelin@gmail.com>

**Re: st: subsetting a matrix by rowname and column name***From:*Austin Nichols <austinnichols@gmail.com>

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