Dear Jean-Paul, Have a look at the weights argument in ?lm. This should do the trick:
lm(agri ~poly(x, y, degree = 2), data = yourDataFrameName, weights = var_agri) HTH, Thierry ------------------------------------------------------------------------ ---- ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest Cel biometrie, methodologie en kwaliteitszorg / Section biometrics, methodology and quality assurance Gaverstraat 4 9500 Geraardsbergen Belgium tel. + 32 54/436 185 [EMAIL PROTECTED] www.inbo.be To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher The plural of anecdote is not data. ~ Roger Brinner The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. ~ John Tukey -----Oorspronkelijk bericht----- Van: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Namens Jean-Paul Kibambe Lubamba Verzonden: dinsdag 2 september 2008 15:21 Aan: [email protected] Onderwerp: [R-sig-Geo] Weighted linear regression Hi, I am trying to explain some of my variables using a weighted linear regression, with x and y-coordinates as my explanatory variables. For example, I want to explain my variable 'agri' in the following way : agri = x + y + x*y+ x^2 + y^2 where x and y are my coordinates and the regression must be weighted by the variance. How can I do it ? Thanks in advance ! JP For illustration, here is a part of my database (var_agri = variance) agri se_agri var_agri x y 1 -1.04E-05 4.47E-06 2.00E-11 23.78230555 2.968836238 2 -1.01E-05 4.36E-06 1.90E-11 26.05798185 4.476217345 3 -9.47E-06 4.55E-06 2.07E-11 30.5248107 3.058706843 4 -1.00E-05 4.22E-06 1.78E-11 26.97325452 0.737615804 5 -9.96E-06 3.74E-06 1.40E-11 17.67392327 -3.908029603 6 -1.05E-05 4.44E-06 1.97E-11 25.92926863 3.114662312 7 -1.01E-05 4.35E-06 1.89E-11 25.4312434 1.572565497 8 -6.54E-06 4.38E-06 1.92E-11 20.07104333 1.048456276 9 -9.65E-06 4.38E-06 1.91E-11 23.92598192 1.728975609 10 -7.39E-06 4.20E-06 1.76E-11 21.2291592 0.489260168 _______________________________________________ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo Dit bericht en eventuele bijlagen geven enkel de visie van de schrijver weer en binden het INBO onder geen enkel beding, zolang dit bericht niet bevestigd is door een geldig ondertekend document. The views expressed in this message and any annex are purely those of the writer and may not be regarded as stating an official position of INBO, as long as the message is not confirmed by a duly signed document _______________________________________________ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
