rbind two different data frames that have different column names

I want to rbind two different data frames that have different column names

DF1 has 4 columns

DF2 has 3 columns

I want to create DF3 that has DF2 pasted above the DF1 rows in both columns (c3, c4)

The simplest way would be to simply duplicate the column Prec_CAN_45 in df2 and rename it to Prec_CAN_85. Then you can use rbind to combine the two data tables.

Here's an easy dplyr solution:

library(dplyr)

df2 <- df2 %>% dplyr::mutate(Prec_CAN_85 = Prec_CAN_45)

df3 <- rbind(df2, df1)

df3
#>    Year Month Prec_CAN_45 Prec_CAN_85
#>   <dbl> <chr>       <dbl>       <dbl>
#> 1  1998 Jan           0.3        0.3 
#> 2  2014 Jan           0.4        0.4 
#> 3  2015 Jan           0.5        0.65
#> 4  2100 Jan           0.6        0.75

Similarly, a base R solution might look like:

df2$Prec_CAN_85 <- df2$Prec_CAN_45

df3 <- rbind(df2, df1)

df3
#>    Year Month Prec_CAN_45 Prec_CAN_85
#>   <dbl> <chr>       <dbl>       <dbl>
#> 1  1998 Jan           0.3        0.3 
#> 2  2014 Jan           0.4        0.4 
#> 3  2015 Jan           0.5        0.65
#> 4  2100 Jan           0.6        0.75