[R] help usin scan on large matrix (caveats to what has been discussed before)

[Peter Dalgaard]

Martin Tomko wrote:
> Hi Peter,
> apologies, too fast copying and pasting.
> So, here is the explanation:
> f<-"C:/test/mytab.txt";
> R<-readLines(con=f);
> 
> where mytab.txt is a table formatted as noted in previous post (space 
> delimited, with header, rownames, containing integers).
> 
> Now, my understandign of scan was that I have to specify the FULL number 
> of values in it (examples specify things like 200*2000 for a matrix 
> etc). That's why I thought that I need to do cols*rows as well. Avoiding 
> the first line with headers is simple, avoiding the first column is not 
> - hence my questions.
> Sorry, the corrected, matching parentheses are here - why did the 
> previous execute is a wonder...
> c<-scan(file=f,what=rep(c(list(NULL),rep(list(0L),cols-1)),rows-1), skip=1)
> here, my reasoning was:
> 
> * c(list(NULL),rep(list(0L),cols-1)) specifies a template for any line 
> (first elelement to be ignored => NULL, it is a string in the table 
> specified, and then a repetition of integers - I am still not sure how 
> you derived 0L, and what it means and where to find a doc for that.);
> * the previous needs to be repeated rows-1 times, hence 
> what=rep(c(list(NULL),rep(list(0L),cols-1)),rows-1)
> 
> I do nto understand the following:
> 
>   You need an unlist(c). And more than likely NOT byrow=TRUE. However, I think do.call(cbind,c) should do the trick more easily.
> 
> what will unlist(c) do; why should it not be bywrow=TRUE, and how would 
> you go about integrating do.call(cbind,c) with matrix. Apologies to 
> naive questions, I am a newbie, in principle.
> 

At this point I think you need to actually try my suggestions, and maybe
read the documentation again. Explaining how you have misunderstood the
documentation is not going to help...

-- 
Peter Dalgaard
Center for Statistics, Copenhagen Business School
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com