merge/combine columns with same name but incomplete data

Question

I have two data frames that have some columns with the same names and others with different names. The data frames look something like this:

df1
      ID hel         


        

Answer 1

Here's another data.table approach using binary merge

library(data.table)
setkey(setDT(df1), ID) ; setkey(setDT(df2), ID) # Converting to data.table objects and setting keys
df1 <- df1[df2][, `:=`(i.hello = NULL, i.world = NULL)] # Full left join
df1[df2[complete.cases(df2)], `:=`(hello = i.hello, world = i.world)][] # Joining only on non-missing values
#    ID hello world football baseball hockey soccer
# 1:  1     2     3       43        6      7      4
# 2:  2     5     1       24       32      2      5
# 3:  3    10     8        2       23      8     23
# 4:  4     4    17        5       15      5     12
# 5:  5     9     7       12       23      3     43