Merging rows with shared information

Question

I have a data.frame with several rows which come from a merge which are not completely merged:

b <- read.table(text = \"
      ID   Age    Steatosis               


        

Answer 1

While I'm sure that it's possible with dplyr or tidyr, here's a data.table solution:

b <- read.table(text = "
      ID   Age    Steatosis       Mallory Lille_dico Lille_3 Bili.AHHS2cat
                68 HA-09   16                           5             NA
                69 HA-09   16   <33% no/occasional             NA             1",
                na.strings = c("NA", ""))

keycols <- c("ID", "Age")
library(data.table)
b_dt <- data.table(b)

filter_nas <- function(x){
  if(all(is.na(x))){
    return(unique(x))
  }
  return(unique(x[!is.na(x)]))
}

b_dt[, lapply(.SD, filter_nas ), by = mget(keycols)]


      ID Age Steatosis       Mallory Lille_dico Lille_3 Bili.AHHS2cat
1: HA-09  16      <33% no/occasional         NA       5             1

Note, this only works if the keys are unique.