Applying tidyr separate only to specific rows

问题

I'm trying to use tidyr to separate one column in my data frame, while applying it only to specific rows. While dplyr::filter does the job, it omits the rest of my data. Is there a clean way to apply tidyr to specific rows while keeping the rest of the data untouched?

here is an example of my problem:

#creating DF for the example
df<-data.frame(var_a=letters[1:5],
               var_b=c(sample(1:100,5)),
               text=c("foo_bla","here_do","oh_yes","baa","land"))

gives me this:

  var_a var_b    text
1     a    10 foo_bla
2     b    58 here_do
3     c    34  oh_yes
4     d     1     baa
5     e    47    land

#separating one col:
clean_df<-df %>% separate(text,into=c("first","sec"),sep="_",remove=F)
clean_df

  var_a var_b    text first  sec
1     a    10 foo_bla   foo  bla
2     b    58 here_do  here   do
3     c    34  oh_yes    oh  yes
4     d     1     baa   baa <NA>
5     e    47    land  land <NA>

I want to split only the "here_do" row. Thanks in advance for any kind of help!

回答1:

Another approach:

cols_to_split = c('here_do')

clean_df <-df %>% 
     filter(text %in% cols_to_split) %>% 
     tidyr::separate(text,into=c("first","sec"),sep="_",remove=F) %>% 
     bind_rows(filter(df, !text %in% cols_to_split))


#  var_a var_b    text first  sec
#1     b     7 here_do  here   do
#2     a    26 foo_bla  <NA> <NA>
#3     c    23  oh_yes  <NA> <NA>
#4     d     2     baa  <NA> <NA>
#5     e    67    land  <NA> <NA>

If you need to keep rest of the rows in column 'first', you may use:

clean_df <-df %>% 
     filter(text %in% cols_to_split) %>% 
     tidyr::separate(text,into=c("first","sec"),sep="_",remove=F) %>% 
     bind_rows(filter(df, !text %in% cols_to_split)) %>% 
     mutate(first = ifelse(is.na(first), as.character(text), first))

#  var_a var_b    text   first  sec
#1     b     7 here_do    here   do
#2     a    26 foo_bla foo_bla <NA>
#3     c    23  oh_yes  oh_yes <NA>
#4     d     2     baa     baa <NA>
#5     e    67    land    land <NA>

回答2:

We can do this in base R by replacing the delimiter for the 'here_do' in the 'text' column i.e. change it to 'here,do' using sub, read it with read.csv and cbind with the original dataset

cbind(df,  read.csv(text=sub("(?<=here)_(?=do)", ",", df$text,
       perl = TRUE), header=FALSE, col.names = c("first", "sec")))
#  var_a var_b    text   first sec
#1     a    93 foo_bla foo_bla    
#2     b    51 here_do    here  do
#3     c    65  oh_yes  oh_yes    
#4     d    70     baa     baa    
#5     e    32    land    land

Or if we need a tidyr solution, use the extract

library(tidyr)
extract(df, text, into = c("first", "sec"), "(here)_(do)", remove = FALSE)
#  var_a var_b    text first  sec
#1     a    93 foo_bla  <NA> <NA>
#2     b    51 here_do  here   do
#3     c    65  oh_yes  <NA> <NA>
#4     d    70     baa  <NA> <NA>
#5     e    32    land  <NA> <NA>

来源：https://stackoverflow.com/questions/41506310/applying-tidyr-separate-only-to-specific-rows

标签

dataframe

tidyr