I have two dataframes each containing lists of dates in columns and I need to find the difference in between these dates in days by comparing each column against each other. The number of columns in each data frame can vary so I’d like to code to be flexible enough to handle this.

I can create a new column which determines the number of days between two columns on the same dataset using the following

DF.Out<-mutate(DF, DF=as.numeric(difftime(DF$Date_1,DF$Date_2, units = "d")))

but have been unable to expand this to handle my current problem I guess I need to use lapply or similar? See an example of input and desired output below

Input Dataframe1:

Input Dataframe2:

Desired Output

>Solution :

We could use outer

df1[] <- lapply(df1, as.Date, format = "%d/%m/%Y")
df2[] <- lapply(df2, as.Date, format = "%d/%m/%Y")
f1 <- Vectorize(function(x, y) list(as.numeric(difftime(y, x, units = "d"))))
m1 <- outer(df1, df2, FUN = f1)
            df2_Date1 df2_Date2 df2_Date3
df1_Date1      3, 1      4, 5     0, 12
df1_Date2    -2, -1     -1, 3    -5, 10
as.data.frame(setNames(c(m1), do.call(paste, 
   c(expand.grid(dimnames(m1)), sep = " v "))))

-output

   df1_Date1.v.df2_Date1 df1_Date2.v.df2_Date1 df1_Date1.v.df2_Date2 df1_Date2.v.df2_Date2 df1_Date1.v.df2_Date3 df1_Date2.v.df2_Date3
1                     3                    -2                     4                    -1                     0                    -5
2                     1                    -1                     5                     3                    12                    10

data

df1 <- structure(list(df1_Date1 = c("20/1/2023", "15/1/2023"), df1_Date2 = c("25/1/2023", 
"17/1/2023")), class = "data.frame", row.names = c(NA, -2L))

df2 <- structure(list(df2_Date1 = c("23/1/2023", "16/1/2023"), df2_Date2 = c("24/1/2023", 
"20/1/2023"), df2_Date3 = c("20/1/2023", "27/1/2023")), class = "data.frame", row.names = c(NA, 
-2L))