Hello Well, the problem is, that arcilla is the percentage of clay in the soil sample. So, for linear model, I need to work with that number or value. Now, R thinks that arcilla (arcilla means clay in spanish), is a factor, and gives me the value as a factor, so the output of the linear model is Call: lm(formula = formula, data = caperf)
Residuals: Min 1Q Median 3Q Max -1.466e+01 -1.376e-15 1.780e-16 2.038e-15 1.279e+01 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 1.68964 6.33889 0.267 0.790221 arcilla0.9 1.90228 8.90888 0.214 0.831239 arcilla10 1.26371 7.96734 0.159 0.874212 arcilla10.3 15.70081 9.05141 1.735 0.085090 . arcilla10.4 7.27517 7.72806 0.941 0.348183 arcilla10.45 7.03879 9.02600 0.780 0.436853 arcilla10.5 2.41241 8.90827 0.271 0.786954 arcilla10.65 15.44298 9.03879 1.709 0.089838 . arcilla10.7 19.35651 9.04675 2.140 0.034185 * arcilla10.9 3.55947 9.18501 0.388 0.698974 [...] arcilla9.9 6.31949 7.35724 0.859 0.391892 arcilla#N/A 24.17959 8.87201 2.725 0.007274 ** limo 0.24920 0.04605 5.412 2.76e-07 *** CO_gkg1 0.21015 0.03931 5.346 3.73e-07 *** C03Ca 0.01711 0.02727 0.628 0.531337 --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Residual standard error: 6.249 on 135 degrees of freedom (50 observations deleted due to missingness) Multiple R-squared: 0.9736, Adjusted R-squared: 0.9014 F-statistic: 13.47 on 370 and 135 DF, p-value: < 2.2e-16 So, in the desired linear model, arcilla should be just a line, with the valors of the linear model. I hope you understand better more. If not, I could make an english version of the file to send, so you can try the commands. Thanks a lot for your help! Arantzazu Blanco Bernardeau Dpto de Química Agrícola, Geología y Edafología Universidad de Murcia-Campus de Espinardo ---------------------------------------- > Date: Tue, 18 May 2010 11:54:20 -0400 > Subject: Re: [R] (no subject) > From: mailinglist.honey...@gmail.com > To: aramu...@hotmail.com > CC: r-help@r-project.org > > Hi, > > Sorry, I'm not really getting what going on here ... perhaps having > more domain knowledge would help me make better sense of our question. > > In particular: > > On Tue, May 18, 2010 at 11:35 AM, Arantzazu Blanco Bernardeau > wrote: >> >> Hello >> I have a data array with soil variables (caperf), in which the variable >> "clay" is factor (as I see entering str(caperf)) . I need to do a regression >> model, so I need to have arcilla (=clay) as a numeric variable. For that I >> have entered >> >> as.numeric(as.character(arcilla)) >> >> and even entering >> 'as.numeric(levels(arcilla))[arcilla]' > > The above code doesn't make sense to me ... > > Perhaps cleaning up your question and providing some reproducible > example we can use to help show you the light (just describing what a > variable has isn't enough -- give us minimal code we can paste into R > that reproduces your problem). > > Alternatively, depending no what your "levels" mean, you might want to > recode your data using "dummy variables" (I'm not sure if that's the > official term) .. this is what I mean: > > http://dss.princeton.edu/online_help/analysis/dummy_variables.htm > > In your example, let's say you have four levels for "clay" ... maybe > "soft", "hard", "smooth", "red" > > Instead of only using 1 variable with values 1-4, you would recode > this into 4 variables with values 0,1 > > So, if one example has a value of "smooth" for clay. Instead of coding it > like: > clay: 3 > > You would do: > soft: 0 > hard: 0 > smooth: 1 > red : 0 > > -steve > -- > Steve Lianoglou > Graduate Student: Computational Systems Biology > | Memorial Sloan-Kettering Cancer Center > | Weill Medical College of Cornell University > Contact Info: http://cbio.mskcc.org/~lianos/contact _________________________________________________________________ Consejos para seducir ¿Puedes conocer gente nueva a través de Internet? ¡Regístrate ya! ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
