[R] 2 simple questions

Uwe Ligges ligges at statistik.uni-dortmund.de
Fri May 6 17:42:30 CEST 2005

sms13+ at pitt.edu wrote:

> Please excuse what I'm sure are very easy questions but I'm relatively 
> new to the R environment.
> How can I view a range of list elements, but not all.  e.g., I had a 
> matrix of patients and then split them out by patient id.  I know I can 
> do patlist[[1]] to see the first one, but how can I view, say, the first 
> ten patients?

Use vector indexing on patlist such as
which return a list of the first 10 elements.
Please read the docs on object indexing.

> My other question is how to count how many patients have a record in 
> which a certain condition holds.  E.g., I was trying something like this 
> to get a count:
> ctr<-0
> temp<-lapply(mylist, function(x){is.na(x$date1[1]) & !is.na(x$date2[1])) 
> ctr<-ctr+1})

No, lapply is NOT a loop, instead think vectorized:

   ## at first look at a logical vector, where the condition holds:
   temp <- sapply(mylist, function(x)
       (is.na(x$date1[1]) & !is.na(x$date2[1])))
   ctr <- sum(temp) # and sum that vector

Uwe Ligges

> But I don't think that's working correctly.
> Thanks,
> Steven
> ______________________________________________
> 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