# [R] Update a variable in a dataframe based on variables in another dataframe of a different size

Lopez, Dan lopez235 at llnl.gov
Wed Nov 13 22:29:35 CET 2013

```This is a great solution! Love the conciseness of your solution. And easy to understand.

Thanks again.
Dan

-----Original Message-----
From: arun [mailto:smartpink111 at yahoo.com]
Sent: Monday, November 11, 2013 6:31 PM
To: Lopez, Dan
Subject: Re: [R] Update a variable in a dataframe based on variables in another dataframe of a different size

Hi,
You could use:
H_DF[match(with(T_DF,paste(FY,ID,sep="_")), with(H_DF,paste(FY,ID,sep="_"))),3]<- "TER"
A.K.

On Monday, November 11, 2013 8:51 PM, "Lopez, Dan" <lopez235 at llnl.gov> wrote:
Below is how I am currently doing this. Is there a more efficient way to do this?
The scenario is that I have two dataframes of different sizes. I need to update one binary factor variable in one of those dataframes by matching on two variables. If there is no match keep as is otherwise update. Also the variable being update, TT in this case should remain a binary factor variable (levels='HC','TER')

HTDF2<-merge(H_DF,T_DF,by=c("FY","ID"),all.x=T)
HTDF2\$TT<-factor(ifelse(is.na(HTDF2\$TT.y),HTDF2\$TT.x,HTDF2\$TT.y),labels=c("HC","TER"))
HTDF2<-HTDF2[,-(3:4)]

# REPRODUCIBLE EXAMPLE DATA FOR ABOVE..
> dput(H_DF)
structure(list(FY = structure(c(1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 5L), .Label = c("FY09", "FY10", "FY11", "FY12", "FY13"), class = "factor"),
ID = c(1, 1, 1, 1, 2, 2, 2, 2, 2), TT = structure(c(1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = c("HC", "TER"), class = "factor")), .Names = c("FY", "ID", "TT"), class = "data.frame", row.names = c(1L, 2L, 3L, 4L, 6L, 7L, 9L, 10L, 11L))
> dput(T_DF)
structure(list(FY = structure(c(4L, 2L, 5L), .Label = c("FY09", "FY10", "FY11", "FY12", "FY13"), class = "factor"), ID = c(1, 2, 2), TT = structure(c(2L, 2L, 2L), .Label = c("HC", "TER"), class = "factor")), .Names = c("FY", "ID", "TT"), row.names = c(5L, 8L, 12L), class = "data.frame")

Dan Lopez
LLNL, HRIM - Workforce Analytics & Metrics

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