Dear Barry, You have to rethink the input format. This is easy if you use a matrix.
A <- cbind(A_01, A_02, A_03, A_04) index <- cbind(seq_along(VFD_ID), VFD_ID) A[index] Best regards, ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance Kliniekstraat 25 1070 Anderlecht Belgium + 32 2 525 02 51 + 32 54 43 61 85 thierry.onkel...@inbo.be 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: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] Namens Barry King Verzonden: maandag 29 september 2014 11:59 Aan: r-help@r-project.org Onderwerp: [R] How to get rid of my for loop # Here are sample data, sample vectors, and a for loop # that I am using now. I wish to get rid of the for loop # and use functions and one of the apply functions to # perform the work without needing a many iteration for loop. A_01 <- 1:5 A_02 <- 6:10 A_03 <- 11:15 A_04 <- 16:20 B_01 <- 101:105 B_02 <- 106:110 B_03 <- 111:115 B_04 <- 116:120 # I am showing just two pairs, A_x with A_array and B_x with B_array. # In actuality there are about a dozen such pairings. A_array <- array(NA, dim=5) B_array <- array(NA, dim=5) VFD_ID <- c(3, 2, NA, 1, 3) nobs <- length(VFD_ID) # This for loop works fine but is not appropriate for # a large number of observations in VFD_ID. for (i in 1:nobs){ if (is.na(VFD_ID[i])){ A_array[i]<- 0 B_array[i]<- 0 } else if (VFD_ID[i] == 1){ A_array[i]<-A_01[i] B_array[i]<-B_01[i] } else if (VFD_ID[i] == 2){ A_array[i]<-A_02[i] B_array[i]<-B_02[i] } else if (VFD_ID[i] == 3){ A_array[i]<-A_03[i] B_array[i]<-B_03[i] } else if (VFD_ID[i] == 4){ A_array[i]<-A_04[i] B_array[i]<-B_04[i] } } # This does NOT work. It returns the entire vector, # not just the corresponding element in VFD_ID. # (Note: It seems like a switch function would work here # but I was unable to get it to work correctly.) A_array_fnc <- function(x){ if (is.na(x)) return (0) else if (x == 1) return (A_01) else if (x == 2) return (A_02) else if (x == 3) return (A_03) else if (x == 4) return (A_04) } B_array_fnc <- function(x){ if (is.na(x)) return (0) else if (x == 1) return (B_01) else if (x == 2) return (B_02) else if (x == 3) return (B_03) else if (x == 4) return (B_04) } A_array <- sapply(VFD_ID,A_array_fnc) B_array <- sapply(VFD_ID,B_array_fnc) # Is there a way to write the functions correctly so that # the return value for, say A_array[4] is A_03[4] if VFD_ID == 3? # Any assistance is greatly appreciated. ______________________________________________ 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. * * * * * * * * * * * * * D I S C L A I M E R * * * * * * * * * * * * * 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-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.
