[R] work with a subset of the dataset

[R. Michael Weylandt]

Be careful: I think that's only going to check exact equality: i.e.,
it won't find 20.5, but it also won't find 19.9999999999997 which you
might get when you mean 20 due to floating point error. If the OP has
non-integer data, this will cause trouble.

Michael

PS -- you also don't need the call to `c` -- there's nothing the 20:30
sequence is being combined with.

On Thu, Jan 12, 2012 at 10:50 PM, Schreiber, Stefan
<Stefan.Schreiber at ales.ualberta.ca> wrote:
> Or with what I just learned:
>
>  subset<-[mydata$age %in% c(20:30),]
>
> Thanks for explaining Michael!
>
> Stefan
>
>
>
>
> -----Original Message-----
> From: r-help-bounces at r-project.org on behalf of Marc Schwartz
> Sent: Thu 1/12/2012 8:38 PM
> To: R. Michael Weylandt
> Cc: r-help at r-project.org; manu79
> Subject: Re: [R] work with a subset of the dataset
>
> Presuming that 'DF' is the data frame, I am not sure what is wrong with
>
>   NewDF <- subset(DF, (age >= 20) & (age <= 30))
>
> presuming that 20 and 30 are to be included.
>
> ?
>
> Marc Schwartz
>
> On Jan 12, 2012, at 9:26 PM, R. Michael Weylandt wrote:
>
>> You can probably do it more easily with the subset() function but in
>> my experience that often leads to more problems than solutions:
>> perhaps try this.
>>
>> idx <- with(DATA, which(age > 20 & age < 30))
>> DATA[idx, ]
>>
>> Michael
>>
>> On Thu, Jan 12, 2012 at 5:25 PM, manu79 <manuelespino79 at hotmail.it> wrote:
>>> Hello,
>>> I have a big dataset with many variables and I would like to consider
>>> only
>>> the rows in which there is a specific value of a variable.
>>>
>>> I make an example for explain what I mean:
>>> I have 5 variables describing a person: age, sex, weight, colour of hair,
>>> colour of eyes.
>>> I have 1000 rows (1000 persons) and I want to consider only the persons
>>> whose age is between 20 to 30. How can I do?
>>>
>>> Thank you very much
>>> M.
>
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