R loops for basic data cleaning-CodePudding

I'm a bit new to R and programming in general. I have to clean a lot of data, and often it's a similar issue in multiple columns. So, I would like to use a loop, rather than writing out each line of code. I have data similar to this:

black <- c("1.33%", "9.22%", "10.71%")
white <- c("5.23%", "8.12%", "11.72%")
day <- c("Wednesday", "Thursday", "Friday")
blue <- c("2.21%", "1.12%", "8.79%")
df <- data.frame(black, white, day, blue)

This gets me a dataframe like this:

   black  white       day  blue
1  1.33%  5.23% Wednesday 2.21%
2  9.22%  8.12%  Thursday 1.12%
3 10.71% 11.72%    Friday 8.79%

I have read that there are 'for' loops, and also that the apply() family work like loops in R too... How would I loop through the variables black, white and blue (but not day) so that I can:

remove the % sign
change type from char to numeric
round to 1 decimal place?

Like I say, I would like to know how to write this as both a for loop and apply. To remove the % sign I have used mutate and gsub before...

Thanks for your suggestions, particularly helping me to write legible code! Best, Roger

CodePudding user response：

Here is one tidy way using dplyr

library(dplyr)

clean_my_data<-function(input){
   gsub("%", "", input) %>% as.numeric() %>% round(1)
}

df_new<-df %>%
  mutate(across(c(black,white,blue), clean_my_data))

df_new
#>   black white       day blue
#> 1   1.3   5.2 Wednesday  2.2
#> 2   9.2   8.1  Thursday  1.1
#> 3  10.7  11.7    Friday  8.8

^{Created on 2022-01-15 by the reprex package (v2.0.1)}

CodePudding user response：

this is a quick and dirty way of doing it and it can be improved!

First you need a function that do the job then you apply that function (or you do a loop it is up to you).

clean_color <- function(x) {
# just remove the last char, it can fail on data like that "1.38% "
    without_percent = substr(x, 
                           start = 1, 
                           stop = nchar(x) - 1)
# second part convert in mun and round it
    round(as.numeric(without_percent),1)
        }

Then you apply this function:

sapply(df[,c(1:2,4)], clean_color)