Here is another way:

> xx <- data.frame(P = sample(5, 100, TRUE), M = sample(5, 100, TRUE), id = 1:100)

> require(data.table)

> xx <- data.table(xx) # convert to data.table

> count <- xx[

+ , list(count = length(id))

+ , by = list(M, P)

+ ]

> str(count)

Classes ‘data.table’ and 'data.frame': 24 obs. of 3 variables:

$ M : int 1 1 1 1 1 2 2 2 2 2 ...

$ P : int 1 2 3 4 5 1 2 3 4 5 ...

$ count: int 5 4 3 2 9 3 3 6 3 7 ...

> count

M P count

1 1 5

1 2 4

1 3 3

1 4 2

1 5 9

2 1 3

2 2 3

2 3 6

2 4 3

On Mon, Jul 4, 2011 at 5:48 AM, UriB <

[hidden email]> wrote:

> I have a matrix of claims at year1 that I get simply by

>

> claims<-read.csv(file="Claims.csv")

> qq1<-claims[claims$Year=="Y1",]

>

> I have MemberID and ProviderID for every claim in qq1 both are integers

>

> An example for the type of questions that I want to answer is

> how many times ProviderID number 345 appears together with MemberID 23 in

> the table qq1

>

> In order to answer these questions for every possible ProviderId and every

> possible MemberID

> I would like to have a matrix that has first column as memberID when every

> memberID in qq1 appears only once and columns that have number of appearance

> of ProviderID==i for every i that has

> sum(qq1$ProviderID==i)>0

>

> My question is if there is a simple way to do it in R

> Thanks in Advance

>

> Uri

>

> --

> View this message in context:

http://r.789695.n4.nabble.com/How-to-build-a-matrix-of-number-of-appearance-tp3643248p3643248.html> Sent from the R help mailing list archive at Nabble.com.

>

> ______________________________________________

>

[hidden email] 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.

>

--

Jim Holtman

Data Munger Guru

What is the problem that you are trying to solve?

______________________________________________

[hidden email] mailing list

https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide

http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.