[R] Populating then sorting a matrix and/or data.frame

[Michael Bedward]

All values in a matrix are the same type, so if you've set up a matrix
with a character column then your numeric values will also be stored
as character. That would explain why they are being converted to
factors.  It would also explain why your query isn't working.

Michael


On 11 November 2010 18:40, Noah Silverman <noah at smartmediacorp.com> wrote:
> That was a typo.
>
> It should have read:
> results[results$one < 100,]
>
> It does still fail.
>
> There is ONE column that is text.  So my guess is that R is seeing that and
> assuming that the entire data.frame should be factors.
>
> -N
>
> On 11/10/10 11:16 PM, Michael Bedward wrote:
>>
>> Hello Noah,
>>
>> If you set these names...
>>>
>>> names(results)<- c("one", "two", "three")
>>
>> this won't work...
>>>
>>> results[results$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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>
>