[R] equivalent of excel "sumif"

[Luis Ridao Cruz]

R-help,

I have two data frames df1 and df2:

>head(df1)
  lgdcm 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
     0 0 0 0 0 0 0 0 0 0 0  0  0  0  0  0  0
     1 0 0 0 0 0 0 0 0 0 0  0  0  0  0  0  0
     2 0 0 0 0 0 0 0 0 0 0  0  0  0  0  0  0
     3 0 0 0 0 0 0 0 0 0 0  0  0  0  0  0  0
     4 0 0 0 0 0 0 0 0 0 0  0  0  0  0  0  0
     5 0 0 0 0 0 0 0 0 0 0  0  0  0  0  0  0
...
...

> head(df2)
  lgdcm  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
       34 NA NA  1 NA NA NA NA NA NA NA NA NA NA NA NA NA
       36 NA NA  1 NA NA NA NA NA NA NA NA NA NA NA NA NA
       40 NA NA  1  1 NA NA NA NA NA NA NA NA NA NA NA NA
       41 NA NA NA NA  3 NA NA NA NA NA NA NA NA NA NA NA
       42 NA NA NA NA  7 NA NA NA NA NA NA NA NA NA NA NA
       43 NA NA NA  1  6 NA NA NA NA NA NA NA NA NA NA NA
....
....

I want to fill up the columns of df1 (0,1,2,,,,15)
with columns from df2 (0,1,2,,,,15) with column 'lgdcm' as the
criterion for matching.

There is a function in excel which does this type of thing, something
like:
SUMIF(range,criteria,sum_range)

Can anyone help with this?

Thanks in advance.