[R] Query - Merging and conditional replacement of values in a data frame

[Jeff Newmiller]

Or use rownames and subscripting?

df1 <- read.table( text=
"time v1  v2 v3
1     2   3  4
2     5   6  4
3     1   3  4
4     1   3  4
5     2   3  4
6     2   3  4
",header=TRUE)

df2 <- read.table( text=
"time v11  v12 v13
3     112   3  4
4     112   3  4
",header=TRUE)

df3 <- df1
rownames( df3 ) <- df3$time
df3[ as.character( df2$time ), "v1" ] <- df2[ , "v11" ]
df3
df3[ "7", c( "time", "v1" ) ] <- data.frame( time=7, v1=2 )
df3
df2b <- data.frame( time=c(7,8), v2=c(4,5), v3=c(6,7) )
df2b
df3[ df2b$time, c( "time", "v2", "v3" ) ] <- df2b
df3

On Sat, 11 Feb 2017, Bert Gunter wrote:

> Your "assignments" (<-) are not legitimate R code that can be cut and
> pasted. Learn to use dput() to provide examples that we can use.
>
> You fail to say whether the time column of df2 is a proper subset of
> df1 or may contain times not in df1. I shall assume the latter. You
> also did not say whether the time values occur in order in both data
> frames. I shall assume they do not.
>
> If I understand correctly,then,  match and subscripting will do it,
> something like
>
>
>> df1 <-data.frame(time = 1:6, v1 = c(2,5,1,1,2,2))
>> df2 <- data.frame(time = 4:3,v11 = c(112,113))
>
>> wm <- match(df1$time,df2$time)
>> df1[!is.na(wm),"v1"] <- df2[na.omit(wm),"v11"]
>
>> df1
>
>  time  v1
> 1    1   2
> 2    2   5
> 3    3 113
> 4    4 112
> 5    5   2
> 6    6   2
>
> Cheers,
> Bert
>
>
>
>
>
> Bert Gunter
>
> "The trouble with having an open mind is that people keep coming along
> and sticking things into it."
> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>
>
> On Sat, Feb 11, 2017 at 4:13 PM, Bhaskar Mitra
> <bhaskar.kolkata at gmail.com> wrote:
>> Hello Everyone,
>>
>> I have two data frames df1 and df2 as shown below. They
>> are of different length. However, they have one common column - time.
>>
>> df1 <-
>> time v1  v2 v3
>> 1     2   3  4
>> 2     5   6  4
>> 3     1   3  4
>> 4     1   3  4
>> 5     2   3  4
>> 6     2   3  4
>>
>>
>> df2 <-
>> time v11  v12 v13
>> 3     112   3  4
>> 4     112   3  4
>>
>> By matching the 'time' column in df1 and df2, I am trying to modify column
>> 'v1' in df1 by replacing it
>> with values in column 'v11' in df2. The modified df1 should look something
>> like this:
>>
>> df1 <-
>> time v1   v2 v3
>> 1     2   3  4
>> 2     5   6  4
>> 3     112 3  4
>> 4     112 3  4
>> 5     2   3  4
>> 6     2   3  4
>>
>> I tried to use the 'merge' function to combine df1 and df2 followed by
>> the conditional 'ifelse' statement. However, that doesn't seem to work.
>>
>> Can I replace the values in df1 by not merging the two data frames?
>>
>> Thanks for your help,
>>
>> Regards,
>> Bhaskar
>>
>>         [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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