R help - May 2005 - 2 simple questions

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?

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})

But I don't think that's working correctly.

Thanks,
Steven

Your questions are confusing because you don't seem to understand R's
basic
data structures and manipulations. Please read the "Introduction to R"
manual and appropriate portions of the R languuage definition before
posting.

-- Bert Gunter
Genentech Non-Clinical Statistics
South San Francisco, CA
 
"The business of the statistician is to catalyze the scientific learning
process."  - George E. P. Box
 
 
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of sms13+ at
pitt.edu
> Sent: Friday, May 06, 2005 8:08 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] 2 simple questions
> 
> 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?
> 
> 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})
> 
> 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
>

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
   patlist[1:10]
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