R help - Dec 2007 - expand.grid function

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 
-- 
View this message in context:
http://www.nabble.com/expand.grid-function-tp14484403p14484403.html
Sent from the R help mailing list archive at Nabble.com.

Hi Derek,
On Dec 23, 2007, at 10:59 PM, dxc13 wrote:
>
> 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...
>
Does this do what you want  (x is the matrix)?

do.call(expand.grid, as.data.frame(x))

> 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
Haris Skiadas
Department of Mathematics and Computer Science
Hanover College

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


----- Original Message ----
From: dxc13 <dxc13 at health.state.ny.us>
To: r-help at r-project.org
Sent: Sunday, December 23, 2007 7:59:49 PM
Subject: [R]  expand.grid function



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 
-- 
View this message in context:
 http://www.nabble.com/expand.grid-function-tp14484403p14484403.html
Sent from the R help mailing list archive at Nabble.com.

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