mtb954@gmail.com
2006-Feb-21 17:53 UTC
[R] How to select only certain rows when making a new dataframe?
Dear R-users,
I have two data frames. The "FIRST" data frame has 100 rows, the
"SECOND" data frame has only 50 rows.
The data frames have different variables in columns ("VAR1,"
"VAR2,"
etc) but they share a column called "ID" that contains a unique
identifer linking the two data frames.
I would like to make a "THIRD" data frame containing just the rows of
the "FIRST" data frame that match the rows (on "ID") in the
"SECOND"
data frame.
>THIRD=data.frame(FIRST$ID,FIRST$VAR1,FIRST$VAR2)
How can I modify this line to include in "THIRD" just the rows in
"FIRST" that match the rows in "SECOND"? (i.e., contain the
same value
in the shared "ID" column).
Thanks! Mark
Chuck Cleland
2006-Feb-21 18:06 UTC
[R] How to select only certain rows when making a new dataframe?
THIRD <- merge(FIRST, SECOND, by="ID", all.x=FALSE, all.y=TRUE) mtb954 at gmail.com wrote:> Dear R-users, > > I have two data frames. The "FIRST" data frame has 100 rows, the > "SECOND" data frame has only 50 rows. > > The data frames have different variables in columns ("VAR1," "VAR2," > etc) but they share a column called "ID" that contains a unique > identifer linking the two data frames. > > I would like to make a "THIRD" data frame containing just the rows of > the "FIRST" data frame that match the rows (on "ID") in the "SECOND" > data frame. > >> THIRD=data.frame(FIRST$ID,FIRST$VAR1,FIRST$VAR2) > > How can I modify this line to include in "THIRD" just the rows in > "FIRST" that match the rows in "SECOND"? (i.e., contain the same value > in the shared "ID" column). > > Thanks! Mark > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html-- Chuck Cleland, Ph.D. NDRI, Inc. 71 West 23rd Street, 8th floor New York, NY 10010 tel: (212) 845-4495 (Tu, Th) tel: (732) 452-1424 (M, W, F) fax: (917) 438-0894
Andy Bunn
2006-Feb-21 18:09 UTC
[R] How to select only certain rows when making a new dataframe?
> -----Original Message----- > From: r-help-bounces at stat.math.ethz.ch > [mailto:r-help-bounces at stat.math.ethz.ch]On Behalf Of mtb954 at gmail.com > Sent: Tuesday, February 21, 2006 12:54 PM > To: r-help at stat.math.ethz.ch > Subject: [R] How to select only certain rows when making a new > dataframe? > > > Dear R-users, > > I have two data frames. The "FIRST" data frame has 100 rows, the > "SECOND" data frame has only 50 rows. > > The data frames have different variables in columns ("VAR1," "VAR2," > etc) but they share a column called "ID" that contains a unique > identifer linking the two data frames. > > I would like to make a "THIRD" data frame containing just the rows of > the "FIRST" data frame that match the rows (on "ID") in the "SECOND" > data frame. > > >THIRD=data.frame(FIRST$ID,FIRST$VAR1,FIRST$VAR2) > > How can I modify this line to include in "THIRD" just the rows in > "FIRST" that match the rows in "SECOND"? (i.e., contain the same value > in the shared "ID" column).List this? one <- data.frame(ID = 1:100, Var1 = runif(100), Var2 = runif(100)) two <- data.frame(ID = 26:50, VarA = runif(50), VarB = runif(50)) three <- one[one$ID == two$ID,]
Marco Geraci
2006-Feb-21 21:47 UTC
[R] How to select only certain rows when making a new dataframe?
I think ?merge is what you need. The help page of this function is very....helpful Marco --- mtb954 at gmail.com wrote:> Dear R-users, > > I have two data frames. The "FIRST" data frame has > 100 rows, the > "SECOND" data frame has only 50 rows. > > The data frames have different variables in columns > ("VAR1," "VAR2," > etc) but they share a column called "ID" that > contains a unique > identifer linking the two data frames. > > I would like to make a "THIRD" data frame containing > just the rows of > the "FIRST" data frame that match the rows (on "ID") > in the "SECOND" > data frame. > > >THIRD=data.frame(FIRST$ID,FIRST$VAR1,FIRST$VAR2) > > How can I modify this line to include in "THIRD" > just the rows in > "FIRST" that match the rows in "SECOND"? (i.e., > contain the same value > in the shared "ID" column). > > Thanks! Mark > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html >