Re: data manipulation

[David L Lorenz <lorenz@usgs.gov>]

Jenny,
  You are getting the error because
ID2 is a factor and there is no level "zero." You have 2 choices:
1 redo the ID2 column and add a level "zero" or convert ID2 to
character.
  Note that you can prevent automatic
conversion of character to factor by specifying stringsAsFactors=F
as an argument in data.fame(). You
can also set that as a global option, but probably do not want to.
Dave

"Zheng_Jenny" <Zheng_Jenny@Allergan.com>
Sent by: s-news-owner@lists.biostat.wustl.edu

10/27/2006 01:33 PM

To	<s-news@lists.biostat.wustl.edu>
cc
Subject	[S] data manipulation

Hi, everyone,
Would anyone help me with the problem below?

 
I have a dataset x including ID, Time, DV
and ID2.
 
I can use 
x$DV[x$Time==0]_0 to make DV=0 when
Time is 0 but when I was trying to use command “x$ID2[x$Time==0]_"zero"”
to make ID2==zero when Time is 0, I received the following message”
 
Warning messages:
  replacement values not all in
levels(x): NA's generated in: .A0[x$Time ==
   0]  <-  "zero"
 
Why is that? How can I do what I want
to do? What would be effective command to change DV=0 when time is 0,2
and 4. Thanks in advance.
 
 
 
Jenny
 
 
x_data.frame(ID=seq(1,10,1),Time=rep(c(0,1,2,3,4),2),DV=rnorm(10,0,1),ID2=rep(sample(letters,5),2))
x$DV[x$Time==0]_0
x$ID2[x$Time==0]_"zero"
Warning messages:
  replacement values not all in
levels(x): NA's generated in: .A0[x$Time ==
   0]  <-  "zero"