On Jul 25, 2011, at 6:48 PM, William Dunlap wrote:
-----Original Message-----
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org
] On Behalf Of David Winsemius
Sent: Monday, July 25, 2011 3:39 PM
To: Anthony Damico
Cc: r-help@r-project.org
Subject: Re: [R] Recoding Multiple Variables in a Data Frame in One
Step
On Jul 21, 2011, at 8:06 PM, Anthony Damico wrote:
Hi, I can't for the life of me find how to do this in base R, but
I'd be
surprised if it's not possible.
I'm just trying to replace multiple columns at once in a data frame.
#load example data
data(api)
#this displays the three columns and eight rows i'd like to replace
apiclus1[ apiclus1$meals > 98 , c( "pcttest" , "api00" ,
"sch.wide" ) ]
#the goal is to replace pcttest with 100, api100 with NA, and
sch.wide with
"Maybe"
#this doesn't work--
apiclus1[ apiclus1$meals > 98 , c( "pcttest" , "api00" ,
"sch.wide" ) ] <-
c( 100 , NA , "Maybe" )
Try list(pcttest=100, api00=NA, sch.wide="Maybe") instead
of c(100, NA, "Maybe") as the new value.
Here is a self-contained example
df <- data.frame(Size=sin(1:10), Name=state.name[11:20],
Value=11:20, stringsAsFactors=FALSE)
df[df$Size<0, c("Name", "Value")] <- list(Name="JUNK", Value=-99)
df
Anthony, Notice that Bill's solution , besides being error-free which
mine wasn't, also allows you to mix data classes in your replacements,
which mine would not have allowed you to to since the replacement was
a single vector.
df[df$Size<0, c("Name", "Value")] <- rep( c( "JUNK" , -99 ),
each = sum(df$Size < 0)
) # not exactly what I posted,
but the same idea
df
Size Name Value
1 0.8414710 Hawaii 11
2 0.9092974 Idaho 12
3 0.1411200 Illinois 13
4 -0.7568025 JUNK -99
5 -0.9589243 JUNK -99
6 -0.2794155 JUNK -99
7 0.6569866 Kentucky 17
8 0.9893582 Louisiana 18
9 0.4121185 Maine 19
10 -0.5440211 JUNK -99
str(df$Value )
# chr [1:10] "11" "12" "13" "-99" "-99" "-99" "17" "18" "19" "-99"
What appeared to be a solution was in fact only able to do so by
coercing "df$Value" to a character vector.
--
David.
Size Name Value
1 0.8414710 Hawaii 11
2 0.9092974 Idaho 12
3 0.1411200 Illinois 13
4 -0.7568025 JUNK -99
5 -0.9589243 JUNK -99
6 -0.2794155 JUNK -99
7 0.6569866 Kentucky 17
8 0.9893582 Louisiana 18
9 0.4121185 Maine 19
10 -0.5440211 JUNK -99
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
#the results replace downward instead of across
apiclus1[ apiclus1$meals > 98 , c( "pcttest" , "api00" ,
"sch.wide" ) ]
If I had noted that I would have tried this:
apiclus1[ apiclus1$meals > 98 , rep( c( "pcttest" , "api00" ,
"sch.wide" ),
each = sum(apiclus1$meals >
98)
) ]
Should be pretty easy to test, but since _you_ are the one
responsible
for providing examples for testing when posting to rhelp, I am going
to throw an untested theory back at you.
I know I can do this with a few more steps (like one variable at a
time or
by counting the number of rows to replace and then using rep() ..but
I'm
hoping there's a quicker way?
Thanks!!
Anthony Damico
David Winsemius, MD
West Hartford, CT
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