Hmm. I think this could be faster still:
tab1 <- with(pisa1, table(CNT,GENDER,ISCOF,ISCOM))
tab3 <- rowSums(tab1 == 1)
but check it...
Bill Venables
CSIRO Laboratories
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http://www.cmis.csiro.au/bill.venables/
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Venables, Bill (CMIS, Cleveland)
Sent: Thursday, 14 February 2008 10:30 AM
To: [EMAIL PROTECTED]; [EMAIL PROTECTED]
Subject: Re: [R] apply on large arrays
Your code is
tab1 <- with(pisa1, table(CNT,GENDER,ISCOF,ISCOM))
tab2 <- apply(tab1, 1:4,
function(x) ifelse(sum(x) == 1, 1, 0))
tab3 <- apply(tab2, 1, sum)
As far as I can see, step 2, (the problematic one), merely replaces any
entries in tab1 that are not equal to one by zeros. I think this would
do the same job a bit faster:
tab2 <- tab1 <- with(pisa1, table(CNT,GENDER,ISCOF,ISCOM))
tab2[] <- 0
tab2[which(tab1 == 1, arr.ind = TRUE)] <- 1
tab3 <- rowSums(tab2)
If you don't need to keep tab1, you would make things even better by
removing it.
Bill Venables.
Bill Venables
CSIRO Laboratories
PO Box 120, Cleveland, 4163
AUSTRALIA
Office Phone (email preferred): +61 7 3826 7251
Fax (if absolutely necessary): +61 7 3826 7304
Mobile: +61 4 8819 4402
Home Phone: +61 7 3286 7700
mailto:[EMAIL PROTECTED]
http://www.cmis.csiro.au/bill.venables/
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Erich Neuwirth
Sent: Thursday, 14 February 2008 9:52 AM
To: r-help
Subject: [R] apply on large arrays
I have a big contingency table, approximately of size 60*2*500*500,
and I need to count the number of cells containing a count of 1 for each
of the factors values defining the first dimension.
Here is my attempt:
tab1<-with(pisa1,table(CNT,GENDER,ISCOF,ISCOM))
tab2<-apply(tab1,1:4,function(x)ifelse(sum(x)==1,1,0))
tab3<-apply(tab2,1,sum)
Computing tab2 is very slow.
Is there a faster and/or more elegant way of doing this?
--
Erich Neuwirth, University of Vienna
Faculty of Computer Science
Computer Supported Didactics Working Group
Visit our SunSITE at http://sunsite.univie.ac.at
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______________________________________________
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PLEASE do read the posting guide
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and provide commented, minimal, self-contained, reproducible code.
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
