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From |
Aaron Kirkman <ak1795mailserv@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: Is there a way to use or emulate the behaviour of --predict-- with --by-- groups? |

Date |
Tue, 30 Oct 2012 19:40:58 -0500 |

Dear Statalist, I have data grouped by a variable called --group--, in this example, and I'm trying to use logarithmic interpolation on another variable. Linear interpolation using the --ipolate-- command works perfectly in --by-- group, as shown: **** clear quietly input str1 group x y A 1 1000 A 2 . A 3 3000 A 4 . B 5 45 B 6 . B 9 20 end bysort group: ipolate y x, g(y_linear) e list, noobs sepby(group) **** Unfortunately, this does not work with logarithmic interpolation and --regress--/--predict--. **** gen lgx = log(x) bysort group: regress y lgx by group: predict y_loginterp, xb **** This returns error r(190): "predict may not be combined with by." I know I can use matrix commands to save these variables in the dataset if I'm not using --by--: **** regress y lgx matrix beta = e(b) svmat double beta, names(matcol) list, clean noobs ** group x y lgx betalgx beta_cons A 1 1000 0 -602.68868 1755.3384 A 2 . .6931472 . . A 3 3000 1.098612 . . A 4 . 1.386294 . . B 5 45 1.609438 . . B 6 . 1.791759 . . B 9 20 2.197225 . . Unfortunately, this only stores the values of beta for the last regression run, where group == "B". Is there a way to perform what I'm trying to do? The actual data set is much larger and would probably involve several hundred regressions of this type. Thank you, Aaron * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: Is there a way to use or emulate the behaviour of --predict-- with --by-- groups?***From:*Maarten Buis <maartenlbuis@gmail.com>

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