[R] How to set a filter during reading tables

[guox at ucalgary.ca]

Since there are many rows, using read.table we spent too much on reading
in rows that we do not want. We are wondering if there is a way to read
only rows that we are interested in. Thanks,

-james
> I think you can use readLines(n=1) in loop to skip unwanted rows.
>
> On Mon, Jun 1, 2009 at 12:56 AM,  <guox at ucalgary.ca> wrote:
>> Thanks, Juliet.
>> It works for filtering columns.
>> I am also wondering if there is a way to filter rows.
>> Thanks again.
>> -james
>>
>>> One can use colClasses to set which columns get read in. For the
>>> columns you don't
>>> want you can set those to NULL. For example,
>>>
>>> cc <- c("NULL",rep("numeric",9))
>>>
>>> myData <-
>>> read.table("myFile.txt",header=TRUE,colClasses=cc,nrow=numRows).
>>>
>>>
>>> On Wed, May 27, 2009 at 12:27 PM, Â <guox at ucalgary.ca> wrote:
>>>> We are reading big tables, such as,
>>>>
>>>> Chemicals <-
>>>> read.table('ftp://ftp.bls.gov/pub/time.series/wp/wp.data.7.Chemicals',header
>>>> = TRUE, sep = '\t', as.is =T)
>>>>
>>>> I was wondering if it is possible to set a filter during loading so
>>>> that
>>>> we just load what we want not the whole table each time. Thanks,
>>>>
>>>> -james
>>>>
>>>> ______________________________________________
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>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> PLEASE do read the posting guide
>>>> http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>
>>>
>>>
>>>
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>
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