Comparing data.frames in R

Question

I have 2 data frames

> a1
v1  v2  v3
ABCA1   --> GIF
ACTA1   --| CSNK2A1
ACTN4   --| HDAC7
ACTN4   --> RARA

> a2
v1  v2  v3
ABCA1   --| GIF
ACTA1   --| CSNK2A1
ABCD2   --| HDAC7
ACTN4   --> XYZ1

I want output where a1$v1 == a2$v1 && a1$v3 == a2$v3 && a1$v2 != a2$v2 . So, the outcome will be:

> a3
ABCA1   --> GIF

Because Row 1 fulfill all those conditions. In row 2 condition 3 is not fulfilled. In row 3 condition 1 is not fulfilled and in row 4 condition 2 is not fulfilled.

Answer 1

If we are comparing the 'v1' column in 'a1' and 'a2' datasets, and use & instead of && , we get the expected output

a1[(a1$v1==a2$v1) & (a1$v3==a2$v3) & (a1$v2 != a2$v2), , drop=FALSE]
#    v1  v2  v3
#1 ABCA1 --> GIF

According to the description from ?"&&"

'&' and '&&' indicate logical AND and '|' and '||' indicate logical OR. The shorter form performs elementwise comparisons in much the same way as arithmetic operators. The longer form evaluates left to right examining only the first element of each vector.

Update

If we need to compare one row in 'a1' against all the rows, we can paste the rows in each datasets using do.call(paste,.. , and loop through lapply on the paste elements of 'a1' and compare against the paste d 'a2' or this can be done using outer .

 lapply(do.call(paste, a1), '==', do.call(paste, a2))

Or

 outer(do.call(paste, a1), do.call(paste, a2), '==')

data

a1 <- structure(list(v1 = c("ABCA1", "ACTA1", "ACTN4", "ACTN4"),
 v2 = c("-->", 
"--|", "--|", "-->"), v3 = c("GIF", "CSNK2A1", "HDAC7", "RARA"
)), .Names = c("v1", "v2", "v3"), class = "data.frame", 
row.names = c(NA, -4L))

a2 <- structure(list(v1 = c("ABCA1", "ACTA1", "ABCD2", "ACTN4"), 
v2 = c("--|", 
"--|", "--|", "-->"), v3 = c("GIF", "CSNK2A1", "HDAC7", "XYZ1"
)), .Names = c("v1", "v2", "v3"), class = "data.frame",
row.names = c(NA, -4L))