[R] matrix logic

[Uwe Ligges]

Tom wrote:
> On Tue, 10 Jan 2006 20:25:23 -0500, r user <ruser2006 at yahoo.com> wrote:
> 
> 
>>I have 2 dataframes, each with 5 columns and 20 rows.
>>They are called data1 and data2.I wish to create a
>>third dataframe called data3, also with 5 columns and
>>20 rows.
>>
>>I want data3 to contains the values in data1 when the
>>value in data1 is not NA.  Otherwise it should contain
>>the values in data2.
>>
>>I have tried afew methids, but they do not seem to
>>work as intended.:
>>
>>data3<-ifelse(is.na(data1)=F,data1,data2)
>>
>>and
>>
>>data3[,]<-ifelse(is.na(data1[,])=F,data1[,],data2[,])
>>
>>Please suggest the â€œbestâ€ way.

"Better" way is to have the Syntax correct:

data3 <- ifelse(is.na(data1), data2, data1)


Please check the archives for almost millions of posts asking more or 
less this question...!


> Not sure about the bast but...
> 
> a<-c(1,2,3,NA,5)
> b<-c(4,4,4,4,4)
> 
> c<-a
> c[which(is.na(a))]<-b[which(is.na(a))]

Why do you want to know which()?

  na <- is.na(a)
  c[na] <- b[na]


Uwe Ligges


> 
> 
> 
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