Function to write class types into data frame columns

Question

I'm trying to build out a function where I can specify column positions and class type.

Using the iris dataset it would look like this:

 magic_class_write <- function(df, col_nos, class_types ){

 fill in the blanks
}



library(tidyverse)

# This is how I do it now

glimpse(iris)

class(iris$Sepal.Length) <- "comma"
class(iris$Petal.Width)  <- "comma"

map(iris, class)


# This is how it will be done with the function
magic_class_write(df = iris, col_nos = c(1, 3), class_types = c("comma", "comma"))

Any ideas?

stefan · Accepted Answer · 2021-02-20 11:03:34Z

1

Using a for loop you could do:

magic_class_write <- function(df, col_nos, class_types ){
  for (i in seq_along(col_nos)) {
    class(df[[col_nos[[i]]]]) <- class_types[[i]]
  }
  df
}

iris1 <- magic_class_write(df = iris, col_nos = c(1, 3), class_types = c("comma", "comma"))
lapply(iris1, class)
#> $Sepal.Length
#> [1] "comma"
#> 
#> $Sepal.Width
#> [1] "numeric"
#> 
#> $Petal.Length
#> [1] "comma"
#> 
#> $Petal.Width
#> [1] "numeric"
#> 
#> $Species
#> [1] "factor"

answered Feb 20, 2021 at 11:03

stefan

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1 Comment

akrun Over a year ago

One of the benefits of using the for loop is not to do the return after the assignment

Ronak Shah · Accepted Answer · 2021-02-20 13:35:42Z

1

Using Map :

magic_class_write <- function(df, col_nos, class_types ){
  df[col_nos] <- Map(`class<-`, df[col_nos], class_types)
  return(df)
}

result <- magic_class_write(iris, c(1, 3), c("comma", "comma"))
sapply(result, class)

#Sepal.Length  Sepal.Width Petal.Length  Petal.Width      Species 
#     "comma"    "numeric"      "comma"    "numeric"     "factor"

answered Feb 20, 2021 at 13:35

Ronak Shah

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