R help - Nov 2010 - Populating then sorting a matrix and/or data.frame

Hi,

I have a process in R that produces a lot of output.  My plan was to 
build up a matrix or data.frame "row by row", so that I'll have a
nice
object with all the resulting data.

I started with:
results <- matrix(ncol=3)
names(results) <- c("one", "two", "three")

Then, when looping through the data:
results <- rbind(results, c(a,b,c))

This seems to work fine. BUT, my problem arises when I want to filter, 
sort, etc.

I tried (thinking like a data.frame):
results[results$c < 100,]

But that fails.

I tried making it a data.frame with
foo <- data.frame(results)

But that converted all the numeric values to factors!!!  Which causes a 
whole mess of problems.

Any ideas??

-N

Hello Noah,

If you set these names...
> names(results) <- c("one", "two", "three")
this won't work...
> results[results$c < 100,]
because you don't have a column called "c" (unless that's just
a typo
in your post).
> I tried making it a data.frame with
> foo <- data.frame(results)
>
> But that converted all the numeric values to factors!!!
Not sure what's going on there. If 'results' is a numeric matrix you
should get a data.frame with numeric cols since under the hood this is
just calling the as.data.frame function.

Michael





On 11 November 2010 16:02, Noah Silverman <noah at smartmediacorp.com>
wrote:
> Hi,
>
> I have a process in R that produces a lot of output. ?My plan was to build
> up a matrix or data.frame "row by row", so that I'll have a
nice object with
> all the resulting data.
>
> I started with:
> results <- matrix(ncol=3)
> names(results) <- c("one", "two", "three")
>
> Then, when looping through the data:
> results <- rbind(results, c(a,b,c))
>
> This seems to work fine. BUT, my problem arises when I want to filter,
sort,
> etc.
>
> I tried (thinking like a data.frame):
> results[results$c < 100,]
>
> But that fails.
>
> I tried making it a data.frame with
> foo <- data.frame(results)
>
> But that converted all the numeric values to factors!!! ?Which causes a
> whole mess of problems.
>
> Any ideas??
>
> -N
>
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