Remove Multiple Empty Columns for String [duplicate]

Question

I have a data table that looks like this:

old1   old2   old3   old4
aaa           ccc
aaa    bbb     
       bbb    ccc    ddd    

I want to remove the empty columns to have something like this:

new1  new2   new3   
aaa   ccc
aaa   bbb     
bbb   ccc    ddd   

I've tried the following which does not work for me:

df[, colSums(df!= "") != ""]
df[!sapply(df, function (x) all(is.na(x) | x == ""))]
Filter(function(x) !(all(x==""|x==0)), df) 

Answer 1

One option using base R apply is to first calculate number of columns which are going to be present in the final dataframe (cols). Filter empty values from each row and insert empty values using rep.

cols <- max(rowSums(df != ""))

as.data.frame(t(apply(df, 1, function(x) {
   vals <- x[x != ""]
   c(vals, rep("", cols - length(vals)))
})))

#   V1  V2  V3
#1 aaa ccc    
#2 aaa bbb    
#3 bbb ccc ddd

---

Another option with gather/spread would be to add a new column for row number convert it to long format using gather, filter the non-empty values, group_by every row and give new column names using paste0 and finally convert it to wide format using spread.

library(dplyr)
library(tidyr)

df %>%
  mutate(row = row_number()) %>%
  gather(key, value, -row) %>%
  filter(value != "") %>%
  group_by(row) %>%
  mutate(key = paste0("new", row_number())) %>%
  spread(key, value, fill = "") %>%
  ungroup() %>%
  select(-row)

#  new1  new2  new3 
#  <chr> <chr> <chr>
#1 aaa   ccc   ""   
#2 aaa   bbb   ""   
#3 bbb   ccc   ddd