Dear Manuel, This is not a matrix versus data-frame issue. The difference is because in the first case you are extracting multiple items at a time, so the column names are attached. But in the second, you are really only extracting individual items, and so the column names are not necessary.
Here's a simple example: DET <- as.matrix(finaldf[,3:6]) # Attaches the column names DET <- as.matrix(finaldf[,3]) # Does not. DET <- as.matrix(finaldf[,c(3, 5)]) # Also does not. DET <- as.data.frame(finaldf[,3:6]) # Also attaches the column names DET <- as.data.framefinaldf[,3]) # Also does not. DET <- as.data.frame(finaldf[,c(3, 5)]) # Also does not. Hope this helps, Phil On 7/20/2012 11:13 AM, Manuel Spínola wrote: > Dear list members, > > I am using function cbind but I got 2 different results, one is a data > frame and the other is a matrix and I would like to undertand why is the > reason: > > I have a data frame called "finaldf" > >> names(finaldf) > [1] "especie" "estrato" "oc1" "oc2" "oc3" "oc4" "oc5" > "oc6" > [9] "oc7" "oc8" "oc9" "oc10" "oc11" "oc12" "oc13" > "oc14" > [17] "oc15" "oc16" "oc17" "oc18" "oc19" "oc20" > > I tried (gave me a data frame): > > DET <- cbind(finaldf[, 3:22]) > >> head(DET) > oc1 oc2 oc3 oc4 oc5 oc6 oc7 oc8 oc9 oc10 oc11 oc12 oc13 oc14 oc15 oc16 > oc17 oc18 > 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 > 0 0 > 27 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 > 0 0 > 53 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 > 2 1 1 1 1 1 1 0 1 1 1 1 1 0 1 0 1 > 1 1 > 28 1 0 1 0 1 1 1 1 1 1 1 1 0 1 1 1 > 1 0 > 54 1 1 1 1 1 1 1 1 0 0 0 1 1 0 1 0 > 0 0 > oc19 oc20 > 1 0 0 > 27 1 0 > 53 0 0 > 2 1 1 > 28 1 0 > 54 0 1 > > and gave me a different results when I tried (gave me a matrix): > > DET <- cbind(finaldf$oc1, finaldf$oc2, finaldf$oc3, finaldf$oc4, > finaldf$oc5, finaldf$oc6, finaldf$oc7, finaldf$oc8, finaldf$oc9, > finaldf$oc10, finaldf$oc11, finaldf$oc12, finaldf$oc13, finaldf$oc14, > finaldf$oc15, finaldf$oc16, finaldf$oc17, finaldf$oc18, finaldf$oc19, > finaldf$oc20) > >> head(DET) > [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12] [,13] > [,14] > [1,] 0 0 0 0 0 0 0 0 1 0 0 0 0 > 0 > [2,] 0 0 0 1 0 0 0 0 0 0 0 0 0 > 0 > [3,] 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 > [4,] 1 1 1 1 1 1 0 1 1 1 1 1 0 > 1 > [5,] 1 0 1 0 1 1 1 1 1 1 1 1 0 > 1 > [6,] 1 1 1 1 1 1 1 1 0 0 0 1 1 > 0 > [,15] [,16] [,17] [,18] [,19] [,20] > [1,] 0 0 0 0 0 0 > [2,] 0 1 0 0 1 0 > [3,] 0 0 0 0 0 0 > [4,] 0 1 1 1 1 1 > [5,] 1 1 1 0 1 0 > [6,] 1 0 0 0 0 1 > > Best, > > Manuel > > > > > _______________________________________________ > R-sig-ecology mailing list > R-sig-ecology@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology [[alternative HTML version deleted]]
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