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From |
Nikolaos Kanellopoulos <nkkanel@yahoo.gr> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Create a row matrix with weighted frequencies from various dummy variables |

Date |
Mon, 4 Jul 2011 07:34:30 +0100 (BST) |

Nick and Maarten, thank you very much for your help. Regards Nikolaos ----- Original Message ---- From: Maarten Buis <maartenlbuis@gmail.com> To: statalist@hsphsun2.harvard.edu Sent: Fri, July 1, 2011 2:01:10 PM Subject: Re: st: Create a row matrix with weighted frequencies from various dummy variables 2011/7/1 Nikolaos Kanellopoulos: > I have two sets of dummy variables (say d1,...,d20 and z1,...,z5) and I want to > create a 1x100 matrix where each element will be the weighted frequency for >each > combination between each d-variable and each z-variable when both equal 1 I think the easiest way to achieve this goal is -collapse- your data. In the example below I used the trick that a frequency is the sum of a "variable" containing only 1s to get the weighted frequency. You can use -mkmat- to turn this into a matrix. You can precede this with -preserve- and end it with -restore- to keep access to the original data. *------------ begin example ---------------- clear set seed 10235 drop _all set obs 1000 /*Generate data*/ gen d = ceil(20*uniform()) gen z = ceil(5*uniform()) generate wt = uniform() gen byte one = 1 collapse (sum) one [pw=wt], by(d z) *--------------- end example ---------------- (For more on examples I sent to the Statalist see: http://www.maartenbuis.nl/example_faq ) Hope this helps, Maarten PS. I presume that the d and z dummies in your example were supposed to represent the different categories in two categorical variables (d and z). In that case the dummies should be mutually exclusive and exhaustive and the way you simulated your data did not achieve that goal. I used tricks from (Buis 2007) to generate these categorical variables. Maarten Buis (2007) "Stata tip 48: Discrete uses for uniform()" The Stata Journal, 7(3): 434-435. <http://www.stata-journal.com/article.html?article=pr0032> -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * 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: Create a row matrix with weighted frequencies from various dummy variables***From:*Nikolaos Kanellopoulos <nkkanel@yahoo.gr>

**Re: st: Create a row matrix with weighted frequencies from various dummy variables***From:*Maarten Buis <maartenlbuis@gmail.com>

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