Re: [R] efficiently diff two data frames

Rui Barradas Tue, 16 Apr 2013 11:18:45 -0700

Hello,

Maybe Petr Savicky's answer in the link


https://stat.ethz.ch/pipermail/r-help/2012-February/304830.html

can lead you to what you want.

I've changed his function a bit in order to return a logical vectorinto the rows where different rows return TRUE.


setdiffDF2 <- function(A, B){
    f <- function(X, Y)
        !duplicated(rbind(Y, X))[nrow(Y) + 1:nrow(X)]
    ix1 <- f(A, B)
    ix2 <- f(B, A)
    ix1 & ix2
}
ix <- setdiffDF2(Xe, Xf)
Xe[ix,]
Xf[ix,]


Note that this gives no information on the columns.
Hope this helps,

Rui Barradas

Em 16-04-2013 18:42, Liviu Andronic escreveu:

Dear all,
What is the quickest and most efficient way to diff two data frames,
so as to obtain a vector of indices (or logical) for rows/columns that
differ in the two data frames?  For example,

Xe <- head(mtcars)
Xf <- head(mtcars)
Xf[2:4,3:5] <- 55
all.equal(Xe, Xf)

[1] "Component 3: Mean relative difference: 0.6863118"
[2] "Component 4: Mean relative difference: 0.4728435"
[3] "Component 5: Mean relative difference: 14.23546"

I could use all.equal(), but it only returns human readable info that
cannot be easily used programmatically. It also gives no info on the
rows. Another way would be to:
require(prob)

setdiff(Xe, Xf)

                 mpg cyl disp  hp drat    wt  qsec vs am gear carb
Mazda RX4 Wag  21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
Datsun 710     22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
Hornet 4 Drive 21.4   6  258 110 3.08 3.215 19.44  1  0    3    1

But again this doesn't return subsetting indices, nor any info on hte
columns. Any suggestions on how to approach this?

Regards ,
Liviu

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