CODEWITHSUNDEEP
rlapplymapply
BIN
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Reputation: 781

How to write a loop or using lapply to create some new variables in R

I have data frame, I want to create some new variables and updated the old ones, but sometimes length of variables are so many, I don't know how to put in a loop or using mapply or lapply.

df <- data.frame(x=c("A","A","A,S"),
                 y=c("12","12,4","10"),
                 z=c("String,Text","Avoid","Use"))
> df
    x    y           z
1   A   12 String,Text
2   A 12,4       Avoid
3 A,S   10         Use

I create some new variables:

df$x_sub <- substring(sub("^[^,]*", "",df$x),2)
df$x     <- sub("\\,.*", "",df$x)
df$y_sub <- substring(sub("^[^,]*", "",df$y),2)
df$y     <- sub("\\,.*", "",df$y)
df$z_sub <- substring(sub("^[^,]*", "",df$z),2)
df$z     <- sub("\\,.*", "",df$z)

The output is correct, but if I have 10 variables, what I need to do to save my time

  x  y      z x_sub y_sub z_sub
1 A 12 String              Text
2 A 12  Avoid           4      
3 A 10    Use     S

Upvotes: 1

Views: 223

Answers (1)

akrun
akrun

Reputation: 886948

We can do this using str_extract

library(stringr)
df1 <- df
df1[] <- lapply(df, function(x) type.convert(str_extract(x, "^[^,]+"), as.is = TRUE))

df1[paste0(names(df1), "_sub")] <-  lapply(df, function(x) 
                   type.convert(str_extract(x, "(?<=,)[^,]+"), as.is = TRUE))
df1
#  x  y      z x_sub y_sub z_sub
#1 A 12 String  <NA>    NA  Text
#2 A 12  Avoid  <NA>     4  <NA>
#3 A 10    Use     S    NA  <NA>

Or another option is cSplit 

library(splitstackshape)
cSplit(df, names(df), ",")
#   x_1 x_2 y_1 y_2    z_1  z_2
#1:   A  NA  12  NA String Text
#2:   A  NA  12   4  Avoid   NA
#3:   A   S  10  NA    Use   NA

Upvotes: 1

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