More informative error messages for R

error_messages.R

# missing variable
`$` <- function(x, y) { var = deparse(substitute(y)); if(!deparse(substitute(y)) %in% names(x)) { stop('missing variable: ', var) }; x[[var]] }

#> prob1<-as.data.frame(cbind(c(1,2,3),c(5,4,3)))
#> colnames(prob1)<-c("Education","Ethnicity")
#> table(prob1$Eduction, prob1$Ethnicity)
# Error in prob1$Eduction : wrong name: Eduction

# error when nrow is used on non data.frames or matrices
nrow <- function(x) { if (is.data.frame(x) || is.matrix(x)) { dim(x)[1L] } else { stop("nrow cannot be used on ", type(x)) } }

#> nrow(prob1$Education)
# Error in nrow(prob1$Education) : nrow cannot be used on double

This is in response to http://rforpublichealth.blogspot.com/2013/01/translating-weird-r-errors.html