Generate combination of data frame and vector

Question

I know expand.grid is to create all combinations of given vectors. But is there a way to generate all combinations of a data frame and a vector by taking each r

Answer 1

You could also do something like this

do.call(rbind,lapply(9:10, function(x,d) data.frame(d, c=x), d=df)))

# or using rbindlist as a fast alternative  to do.call(rbind,list)
library(data.table)
rbindlist(lapply(9:10, function(x,d) data.frame(d, c=x), d=df)))

or

rbindlist(Map(data.frame, c = 9:10, MoreArgs = list(a= 1:3,b=5:7)))

Answer 2

This may not scale when your dataframe has more than two columns per row, but you can just use expand.grid on the first column and then merge the second column in.

df <- data.frame(a = 1:3, b = 5:7)
c <- 9:10
combined <- expand.grid(a=df$a, c=c)
combined <- merge(combined, df)
> combined[order(combined$c), ]
  a  c b
1 1  9 5
3 2  9 6
5 3  9 7
2 1 10 5
4 2 10 6
6 3 10 7

Answer 3

As for me the simplest way is merge(df, as.data.frame(c))

  a b  c
1 1 5  9
2 2 6  9
3 3 7  9
4 1 5 10
5 2 6 10
6 3 7 10