Add a row in a dataframe taking values from a vector R-CodePudding

I have a df like this

df <- data.frame (id = c(123,123,456), w1= c("abc","fgh","kit"), w2 = c("eat","drink","ty"))

   id  w1    w2
1 123 abc   eat
2 123 fgh drink
3 456 kit    ty

and a vector

vec <- c('value1', 'value2').

I would like to add these values to the df when there is a precise correspondance. The final df I'd like to obtain is like this:

   id  w1    w2 new_col
1 123 abc   eat  value1
2 123 abc   eat  value2
3 123 fgh drink  no correspondance
4 456 kit    ty  no correspondance

I tried this code

for (i in 1:length(df$id)) { ## for iterating each row 
  if (df$w2[i] == 'eat') {
    df$new_col[i] <- vec ### how to? Here I need to replace both 'value1' and 'value2' copying the row 
  }
}

Can someone suggest me something? Thanks in advance!

CodePudding user response：

Use tidyr library:

> library(tidyr)
> df[1, 'new_col'] <- toString(vec)
> df %>% separate_rows(new_col)
# A tibble: 4 x 4
     id w1    w2    new_col
  <dbl> <chr> <chr> <chr>  
1   123 abc   eat   value1 
2   123 abc   eat   value2 
3   123 fgh   drink <NA>   
4   456 kit   ty    <NA>   
>

Edit:

> library(tidyr)
> df[1, 'new_col'] <- toString(vec)
> df %>% %>% filter(new_col %in% c('value1', 'value2')) %>% separate_rows(new_col) %>% bind_rows(filter(df, !new_col %in% c('value1', 'value2')))

# A tibble: 4 x 4
     id w1    w2    new_col
  <dbl> <chr> <chr> <chr>  
1   123 abc   eat   value1 
2   123 abc   eat   value2 
3   123 fgh   drink <NA>   
4   456 kit   ty    <NA>   
>

CodePudding user response：

You may add a list column to the dataframe and then use tidyr::unnest to get them as separate rows.

inds <- df$w2 == "eat"
df$new_col[!inds] <- 'no correspondance'
df$new_col[inds] <- list(vec)
tidyr::unnest(df, new_col)

#     id w1    w2    new_col          
#  <dbl> <chr> <chr> <chr>            
#1   123 abc   eat   value1           
#2   123 abc   eat   value2           
#3   123 fgh   drink no correspondance
#4   456 kit   ty    no correspondance