difference of two data frames
It would be useful to have indexed both dataframes with a unique
identifier, such as in rownames etc.
Without that information, you could possibly try to use the same
approach as duplicated() does by "pasting together a character
representation of rows" using "|" (or any other separator).
keys1 <- apply(DF1, 1, paste, collapse="|")
keys1
[1] "1|a" "2|b" "3|c" "4|d" "5|e" "6|f"
duplicated(keys1)
[1] FALSE FALSE FALSE FALSE FALSE FALSE
keys2 <- apply(DF2, 1, paste, collapse="|")
keys2
[1] "1|a" "2|b" "3|c"
duplicated(keys2)
[1] FALSE FALSE FALSE
The duplicated part is neccessary to ensure the key generated is truly
unique. You might want to experiment and see if you can create a unique
key using just a few columns.
keys1 %in% keys2
[1] TRUE TRUE TRUE FALSE FALSE FALSE
w <- setdiff( keys1, keys2 )
DF1[ w, ]
V1 V2
4 4 d
5 5 e
6 6 f
Regards, Adai
joseph wrote:
Hi Jorge
both commands work;
can you extend it to several coulmns? the reason I am asking is that in my real data the uniqueness of the rows is made of all the columns; in other words V1 might have duplicates.
Thanks
----- Original Message ----
From: Jorge Ivan Velez <jorgeivanvelez at gmail.com>
To: joseph <jdsandjd at yahoo.com>
Cc: r-help at r-project.org
Sent: Sunday, September 14, 2008 10:23:33 AM
Subject: Re: [R] difference of two data frames
Hi Joseph,
Try this:
DF1[!DF1$V1%in%DF2$V1,]
subset(DF1,!V1%in%DF2$V1)
HTH,
Jorge
On Sun, Sep 14, 2008 at 12:49 PM, joseph <jdsandjd at yahoo.com> wrote:
Hello
I have 2 data frames DF1 and DF2 where DF2 is a subset of DF1:
DF1= data.frame(V1=1:6, V2= letters[1:6])
DF2= data.frame(V1=1:3, V2= letters[1:3])
How do I create a new data frame of the difference between DF1 and DF2
newDF=data.frame(V1=4:6, V2= letters[4:6])
In my real data, the rows are not in order as in the example I provided.
Thanks much
Joseph
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