[R] creating matrices from lists

[Gregory Ryslik]

Hm,

Now that you mention it, I believe they are factors. They just appeared as 0 or 1 so I treated them as numbers. 

Once I found out they were factors I tried using the as.numeric() but that makes it 1 or 2 as before. How do I actually make it keep the factor number?

Thanks,
Greg
On Sep 20, 2010, at 10:28 PM, David Winsemius wrote:

> 
> On Sep 20, 2010, at 10:12 PM, Gregory Ryslik wrote:
> 
>> Hi,
>> 
>> I have a list of 5 main elements where each main element has 247 atomic entries either 0 or 1. I need to get this into a 247x5 matrix so I do "do.call(cbind, mylist)".  However, it renumbers 0 to a 1 and the 1 to a 2 so that my matrix is filled with 1's and 2's.
>> 
> 
> If I had such a problem I would see if this were more effective:
> 
> matrix(unlist(mylist), length(mylist[[1]]) )
> 
> (There is the column major order default of R matrices.)
> 
>> I understand I can fix it in this case by doing a replace but I would like to avoid that step. Further, sometimes, my list entries will be from 0 to n. I don't want to have to always renumber all the possibilities.
>> 
>> I'm not quite sure why this is going on because when I build the following: l <- list(c(1,2,3),c(1,2,3),c(1,2,3))
>> and execute do.call(cbind, l) it works just fine and there is no renumbering!
> 
> I wouldn't have expected it either, but you only provided an example of what did work. My attempt at reproducing your problem also failed:
> 
> > ll <- list(a=c(1,0,1,1,0), b=c(0,1,0,0,1)  )
> > do.call(cbind, ll)
>     a b
> [1,] 1 0
> [2,] 0 1
> [3,] 1 0
> [4,] 1 0
> [5,] 0 1
> 
> I am wondering if you are dealing with factors and have not looked at your "list" with str(). Haven't tried my method above to see what would happen in tat instance.
> 
> 
> 
>> 
>> Thanks,
>> Greg
>> 	[[alternative HTML version deleted]]
>> 
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> 
> David Winsemius, MD
> West Hartford, CT
>