r - Extract row indices of a dataframe whose entries correspond to rows of another dataframe -

i've been struggling while , can't find way out. here's problem.

i have 2 dataframes:

    df1 <- data.frame(replicate(3,sample(1:10,20,rep=true)))     df1       x1 x2 x3    1  10  1  9    2   3  4  2    3   7  6  8    4   8 10  7    5   5  7  5    6   8  5  9    7   9  8  4    8   6  2  7    9   2  9  6    10  5  2  9    df2 <- data.frame(df1[sample(nrow(df1),4), ])   df2      x1 x2 x3   8   6  2  7   3   7  6  8   10  5  2  9   7   9  8  4 

i create vector x of length(x) = length(df1) containing, per each row of df1, row index of corresponding row in df2 (i.e. same exact values each column between df1 , df2).

consider that:

    dim(df1)     [1] 1096188  3       dim(df2)     [1] 256  3 

and df1 has several rows same values (i.e. corresponding row index same), , in principle rows in df1 should find match row in df2.

the expected output be:

    x    [1] 0 0 2 0 0 0 4 1 0 3 

hope clear enough...

can help?

thanks,

piera

i'd try:

 x <- rownames(df2)[match(do.call(paste, df1), do.call(paste, df2))]  x[is.na(x)] <- 0 

there quite discussion on it's desired output; in @cathg interpretation, line produces it:

 match(do.call(paste, df1), do.call(paste, df2),nomatch=0)