Argthtjtr

I have a table with columns id, colA, and colB. The data contains duplicated id columns where for some rows, colA or colB is null, but its duplicated id has valid values. I want to clean the data so that I remove duplicates, but have complete data. For example my data looks like

id | colA | colB

 1     NA    X

 1      Y    X

 2      Z    NA

 2      Z    Y

 3      Z    Y

 3      Z    Y

 4     NA    NA

 4     NA    NA

and I want my dataframe to look like

id | colA | colB

1     Y      X

2     Z      Y

3     Z      Y

4     NA     NA

I usually use the ifelse statement to replace missing values, but I am confused on how to use this in the context of having duplicated ids.

This answer is very dependent on your actual data being similar in structure to your example data.

Your data:

df1 <- structure(list(id = c(1L, 1L, 2L, 2L, 3L, 3L, 4L, 4L), 

                      colA = c(NA, "Y", "Z", "Z", "Z", "Z", NA, NA), 

                      colB = c("X", "X", NA, "Y", "Y", "Y", NA, NA)), 

                      class = "data.frame", 

                      row.names = c(NA, -8L))

Assuming, as in your example, that each id occurs twice and that where one observation is NA, it is the first observation for that id, then this works:

library(dplyr)

library(tidyr)



df1 %>% 

  group_by(id) %>% 

  fill(colA, colB, .direction = "up") %>%  

  ungroup() %>% 

  distinct()



# A tibble: 4 x 3

     id colA  colB 

  <int> <chr> <chr>

1     1 Y     X    

2     2 Z     Y    

3     3 Z     Y    

4     4 NA    NA 

If the second observation for an id can be NA, you could try adding a second fill after the first one, but this time fill down:

df1 %>% 

  group_by(id) %>% 

  fill(colA, colB, .direction = "up") %>%  

  fill(colA, colB, .direction = "down") %>%  

  ungroup() %>% 

  distinct()

First add a column that tells how many NAs in each row. Then using dplyr, remove duplicated rows first and then for each id keep the row with least missing values -

df$test <- rowSums(is.na(df))



df %>% 

  filter(!duplicated(.)) %>% 

  arrange(id, test) %>% 

  group_by(id) %>% 

  filter(row_number() == 1) %>% 

  ungroup() %>% 

  select(-test)



# A tibble: 4 x 3

     id colA  colB 

  <int> <chr> <chr>

1     1 y     x    

2     2 z     y    

3     3 z     y    

4     4 <NA>  <NA> 

EDIT:
Actually no need to remove duplicates first. Just keeping the row with least missing values for each id should also work -

df$test <- rowSums(is.na(df))



df %>% 

  arrange(id, test) %>% 

  group_by(id) %>% 

  filter(row_number() == 1) %>% 

  ungroup() %>% 

  select(-test)

Data -

df <- data.frame(

  id = c(rep(seq(1:4), each =2)), colA = c(NA, "y", "z", "z", "z", "z", NA, NA), 

  colB = c("x", "x", NA, "y", "y", "y", NA, NA), stringsAsFactors = F)

Creating dataframe - it helps if you post the code to make the sample data

df <- data.frame(id = c(rep(seq(1:4), each =2)), colA = c(NA, "y", "z", "z", "z", "z", NA, NA), colB = c("x", "x", NA, "y", "y", "y", NA, NA))

Removing rows with single NAs

for(i in 1:nrow(df)){



  if(is.na(df[i,]$colA) & !is.na(df[i,]$colB) | !is.na(df[i,]$colA) & is.na(df[i,]$colB)){



df <- df[-i,]



  }

}

Removing remaining duplicates (i.e. double NA rows)

df  <- df[!duplicated(df), ]

Output

df

Probably a more computationally efficient way of doing this but this ought to work.