Re: [R] expand.grid function

From: Satoshi Takahama <brown_emu_at_yahoo.com>
Date: Tue, 25 Dec 2007 01:46:12 -0800 (PST)


Hi Derek,

I love this function as well. If 'mat' is your matrix,
> (mat <- matrix(1:15,ncol=3))

     [,1] [,2] [,3]

[1,]    1    6   11
[2,]    2    7   12
[3,]    3    8   13
[4,]    4    9   14
[5,]    5   10   15

how about
> expandedDF <- do.call(`expand.grid`,as.data.frame(mat))
> head(expandedDF)
  V1 V2 V3
1 1 6 11
2 2 6 11
3 3 6 11
4 4 6 11
5 5 6 11
6 1 7 11
[...]

(the function name can be in backticks, single or double quotes, or passed with no quotes). Hope this helps,

ST

useR's,

I have used expand.grid() several times and like the results it gives  me. I
am now trying something with it that I have not been able to get to  work.
For any n column matrix I would like to run this function on those n  columns
and store the results.
For example, if my matrix has 1 column then this is just expand.grid(x  =
column1). If my matrix has two columns, then I want expand.grid(x = column1, y = column2), and so on for any number of columns...

In a program I am writing, the user can specify any matrix. Does  anyone
know of a way for R to calculate this based on what the input matrix  is?
e.g. if this user gives a 3 column matrix, I want to be able to perform expand.grid() on these 3 columns without having to hard code it b/c I  want
to have this small function embedded in my code and the results stored  as a
variable.

If this isn't clear, I can try to be more detailed. Thank you for any thoughts.

Derek

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Received on Tue 25 Dec 2007 - 09:49:41 GMT

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