[R] Merge two dataframes of different column length and row length by two columns at a time

[Gunther Höning]

Hello,

I have two dataframes of the following structures:

str(a)
`data.frame':   1354896 obs. of  14 variables:
 $ V1 : int  0 1 2 3 4 5 6 7 8 9 ...
 $ V2 : int  0 0 0 0 0 0 0 0 0 0 ...
 $ V3 : int  74 12305 103 12337 46 57 12446 90 12097 79 ...
 $ V4 : num    11.8 1529.2   17.8 1579.4    6.7 ...
 $ V5 : int  88 11040 104 11557 56 58 11040 74 10991 81 ...
 $ V6 : num    15.5 1921.3   20.3 1888.2   12.6 ...
 $ V7 : int  87 8793 90 10142 67 64 9264 73 8589 71 ...
 $ V8 : num    16.0 1750.6   15.2 1783.7   11.0 ...
 $ V9 : int  68 11279 93 11831 43 61 11234 82 10919 76 ...
 $ V10: num    11.5 1999.5   39.0 1842.2    5.0 ...
 $ V11: int  110 12456 92 12063 60 59 12393 82 11831 77 ...
 $ V12: num    21.4 1974.7   33.9 1689.9   10.6 ...
 $ V13: int  81 10887 101 10874 62 74 11115 79 10789 93 ...
 $ V14: num    19.5 1812.3   31.7 1524.1   11.9 ...
> str(b)
`data.frame':   1213901 obs. of  4 variables:
 $ V1: int  0 1 2 3 5 6 7 8 9 10 ...
 $ V2: int  0 0 0 0 0 0 0 0 0 0 ...
 $ V3: Factor w/ 54676 levels "str23","str53",..: 54676 54676 54676 54676
54676 54676 54676 54676 54676 54676 ...
 $ V4: Factor w/ 3 levels "Match","NoMatch",..: 2 2 2 2 2 2 2 2 2 2 ...
> 

I want to merge these dataframes by V1 and V2 of a and b. The combination of
V1, V2 is a unique key.
Note that b is smaller than a.

Any suggestions to solve this problem ?





Gunther Höning

Diplom Physiker
Bioinformatiker

Langenbeckstraße1
55131 Mainz

gunther.hoening at ukmainz.de