[R] List of "occurrence" matrices

[Gabor Grothendieck]

That's a very nice solution. Here is a small tweak
to get the names all at the same time rather than
applying them afterwards:

sapply(levels(unlist(DF)), function(x) crossprod(DF == x), simplify = FALSE)

or

lapply(sapply(levels(unlist(DF)), "==", DF, simplify = FALSE), crossprod)

On Thu, Aug 7, 2008 at 10:03 AM, Dan Davison <davison at stats.ox.ac.uk> wrote:
>
>
> Lauri Nikkinen wrote:
>>
>> R users,
>>
>> I don't know if I can make myself clear but I'll give it a try. I have
>> a data.frame like this
>>
>> x <- "var1,var2,var3,var4
>> a,b,b,a
>> b,b,c,b
>> c,a,a,a
>> a,b,c,c
>> b,a,c,a
>> c,c,b,b
>> a,c,a,b
>> b,c,a,c
>> c,a,b,c"
>> DF <- read.table(textConnection(x),  header=T, sep=",")
>> DF
>>
>> and I would like to sum all the combinations/occurences by a factor
>> (letter in this case) between variables and produce a list of
>> "occurrence" matrices. For example in this case the "occurrence"
>> matrix (first element of list) for factor "a" should look like this
>>
>>>occulist
>> $a
>>       var1    var2    var3    var4
>> var1  x       0       1       1
>> var2  0       x       1       2
>> var3  1       1       x       1
>> var4  1       2       1       x
>>
>> $b
>> etc.
>>
>> because there is two rows where var2 and var4 has "a"
>>
>>
>> I think this does it:
>>
>> occur.matrices <- function(df) {
>>     levels <- levels(unlist(df))
>>     ans <- lapply(levels, function(level) crossprod(df == level))
>>     structure(ans, names=levels)
>> }
>>
>> Dan
>>
>>> occur.matrices(DF)
>> $a
>>      var1 var2 var3 var4
>> var1    3    0    1    1
>> var2    0    3    1    2
>> var3    1    1    3    1
>> var4    1    2    1    3
>>
>> $b
>>      var1 var2 var3 var4
>> var1    3    1    0    1
>> var2    1    3    1    1
>> var3    0    1    3    1
>> var4    1    1    1    3
>>
>> $c
>>      var1 var2 var3 var4
>> var1    3    1    0    1
>> var2    1    3    0    1
>> var3    0    0    3    1
>> var4    1    1    1    3
>>
>>
>>
>> DF[DF$var2=="a" & DF$var4=="a",]
>>
>> Can you give an advice how to achieve this kind of a list of matrices?
>>
>> -Lauri
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>
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>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>