以有效（矢量化）方式用整数替换R中的列中的字符串（值）

Question

I have a big dataframe and I want to replace the values in a column which are character strings with integers. There are more than one thousand unique strings in this column. One way is through a for loop. Here is the code with a toy dataset:

data(mtcars)
library(stringr)
mtcars$gear = as.character(mtcars$gear)
unique_values = unique(mtcars$gear)

for (i in (1:length(unique_values))){

   mtcars$gear =  str_replace(string = mtcars$gear, pattern = unique_values[i], replacement = as.character(i))

}

Is there a more efficient way?

Answer 1

Using the dplyr library should do the trick:

data(mtcars)
library(stringr)
library(dplyr)


mtcars$gear = as.character(mtcars$gear)

mutate(mtcars, gear = as.integer(gear))