It looks like the y2z() function strips NA's so that the vector lengths do not match any longer. The simplest workaround is to remove the NA's. You could do that by using data2 <- na.omit(data) to strip the observations with NA if they will not be used in the rest of the analysis.
If you want to preserve the NAs in the data frame, this seems to work: > nomiss <- complete.cases(data) > data$zeta[nomiss] <- with(data[nomiss, ], y2z(weight, age/12, sex, > ref=who.wgt)) > data sex weight age zeta 1 M 8.5 8 -0.124 2 M 8.2 9 -0.751 3 M 9.0 12 -0.635 4 F NA 9 NA 5 M 5.8 1 2.002 David L. Carlson Department of Anthropology Texas A&M University -----Original Message----- From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Martin Canon Sent: Sunday, October 25, 2015 7:03 AM To: R help <r-help@r-project.org> Subject: [R] y2z question (AGD) Hi to all. I've been trying to calculate weight-for-age z-scores with the y2z command (AGD package). However, I keep getting strange results. My hypothesis is that missings are the problem. My dataframe looks like this: data <- structure(list(sex = structure(c(3L, 3L, 3L, 2L, 3L), .Label = c("", "F", "M"), class = "factor"), weight = c(8.5, 8.2, 9, NA, 5.8), age = c(8, 9, 12, 9, 1)), .Names = c("sex", "weight", "age" ), class = "data.frame", row.names = c(NA, 5L)) Weight is in kg and age in months. I will use WHO curves for children younger than 2 years of age. z-score calculation: library(AGD) data$zeta <- y2z(y = data$weight, x = data$age/12, sex = data$sex, ref = get("who.wgt")) I get: Warning message: In `split<-.default`(`*tmp*`, f, drop = drop, value = value) : number of items to replace is not a multiple of replacement length data$zeta [1] NA NA NA -0.124 NA However a for loop seems to work. for (i in 1:5) { data$zeta[i] <- y2z(y = data$weight[i], x = data$age[i]/12, sex = data$sex[i], ref = get("who.wgt")) } data$zeta [1] -0.124 -0.751 -0.635 NA 2.002 Is there a workaround so that I don't have to use a for loop? na.action doesn't work either. Thanks. Martin ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
