r match and combine into a dataframe multiple vectors of different lengths

April 17, 2023

I am probably missing something very obvious, but I can’t seem to find a way to do this. I would like to will merge multiple vectors (or dataframes?) of different lengths into a dataframe by matching values of vector elements with each other and putting them into same row positions, filling rows left empty with NAs. I have tried the solution from qpcR (cbind.na) but it doesn’t produce expected outcome.

reproducible example:

x<-c("1","2","a","b")
y<-c("1","2","3","4","5","6","b")
z<-c("3","4","5","6","a")

expected output:

x  y  z
[1,]  1 1 NA
[2,]  2 2 NA
[3,] NA 3 3
[4,] NA 4 4
[5,] NA 5 5
[6,] NA 6 6
[7,] a NA a
[8,] b b NA

>Solution :

You could try this. It is similar to the answer by Paul Stafford Allen in that it starts with the unique values. I’ve put them in a list to allow for easy iteration, so it will be straightforward to extend to more columns.

l <- list(x = x, y = y, z = z)

dat <- data.frame(
    unique_vals = sort(unique(unlist(l)))
)

dat[names(l)] <- lapply(l, \(x) {
    x[match(dat$unique_vals, x)]
})

#   unique_vals    x    y    z
# 1           1    1    1 <NA>
# 2           2    2    2 <NA>
# 3           3 <NA>    3    3
# 4           4 <NA>    4    4
# 5           5 <NA>    5    5
# 6           6 <NA>    6    6
# 7           a    a <NA>    a
# 8           b    b    b <NA>

I kept the unique_vals column so it’s clear what’s going on but you may want to remove it.