[R] matrix logic

Uwe Ligges ligges at statistik.uni-dortmund.de
Wed Jan 11 08:47:01 CET 2006

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.:
>>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

>>R-help at stat.math.ethz.ch mailing list
>>PLEASE do read the posting guide!  
> ______________________________________________
> 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

More information about the R-help mailing list