I need to verify that a variable exists in a database. Shiny in R-CodePudding

I have a query that gives me a dataframe. When I receive the data frame, I use this code to make some numeric variables:

variables_numeric<-c("A","B","C","D")
datos[, variables_numeric] <- lapply(datos[, variables_numeric], as.numeric)

But when for some reason one of these columns does not come in the df, I get this error:

Warning: Error in [.data.frame: undefined columns selected

There is some way to avoid this? I was thinking in use ifelse to check first if the dataframe countain the variable.

CodePudding user response：

Maybe you can first find the variables in datos and then apply your code logic:

datos <- data.frame(A = 1, B = 2, C = 3)
variables_numeric <- c("A","B","C","D")
variables_in_df <- variables_numeric[variables_numeric %in% names(datos)]

datos[, variables_in_df] <- lapply(datos[, variables_in_df], as.numeric)