How to convert certain columns only to numeric?

Question

How can I convert certain columns only in a data frame to numeric?

For instance, I have this data frame:

structure(list(airport = c(         


        

Answer 1

1) All your columns is character columns <- sapply(weatherDF, is.character)

airport    xdate       ws       wd humidity 
    TRUE     TRUE     TRUE     TRUE     TRUE

2) Why not simply ?

weatherDF[, 3:ncol(weatherDF)] <- lapply(3:ncol(weatherDF), function(x) as.numeric(weatherDF[[x]]))

or

columns <-c("ws", "wd", "humidity")
weatherDF[, columns] <- lapply(columns, function(x) as.numeric(weatherDF[[x]]))

If your dont know which columns is numeric you can try to find it using tryCatch like

weatherDF[,1:ncol(weatherDF)]=lapply(1:ncol(weatherDF),function(x) {
  tryCatch({
    as.numeric(weatherDF[[x]])
    },warning = function(w) {
    weatherDF[[x]]}
        )} )