[datatable-help] data.table on existing data.frame list

[Irucka Embry]

Hi Matthew, how are you?

Thank you for the notes on fread. I had tried fread to read sitefiles
(see the previous e-mail), but this error message was returned: 

Error in fread(sitefiles) : 
'input' must be a single character string containing a file name, full
path to a file, a URL starting 'http://' or 'file://', or the input data
itself

Is there a work around to get fread to read a file path like sitefiles?

I was detailing what I was doing with read.table to make sure that fread
could also accomplish those same objectives with the files.

Thank you.

Irucka



<-----Original Message-----> 
>From: Matthew Dowle [mdowle at mdowle.plus.com]
>Sent: 8/6/2013 3:49:44 AM
>To: iruckaE at mail2world.com
>Cc: datatable-help at lists.r-forge.r-project.org
>Subject: Re: [datatable-help] data.table on existing data.frame list
>
>On 06/08/13 03:12, iembry wrote:
>> Hi Matthew, thank you for your prompt and great assistance.
>>
>> Yes, moving the autostart = 40 does work. Yes, it did detect the
column
>> names.
>Great.
>>
>> In order to read in the .exsa.rdb files I created a function that
follows
>>
>> getDataRatingDepotFiles <- function (file, hasHeader = TRUE,
separator =
>> "\t")
>> {
>> RDdatatmp <- as.matrix(read.table(file, sep = "\t", fill = TRUE,
>> comment.char = "#", header = T, as.is = TRUE, stringsAsFactors =
FALSE,
>> na.strings = "NA", col.names = c("y", "shift", "x", "stor")))
>> RDdatatmp <- as.matrix(RDdatatmp[c(-1), c(-4)])
>> RDdatatmp <- as.data.frame(RDdatatmp, stringsAsFactors = FALSE)
>> RDdatatmp$y <- as.numeric(as.character(RDdatatmp$y))
>> RDdatatmp$x <- as.numeric(as.character(RDdatatmp$x))
>> RDdatatmp$shift <- as.numeric(as.character(RDdatatmp$shift))
>> return(RDdatatmp)
>> }
>>
>> I created an object called sitefiles that has the pattern of the file
>> extension that I want. In the same folder there are files with two
other
>> file extensions that I do not want to use in this project.
>>
>> sitefiles <- list.files(path ="/tried", pattern <- ".exsa.rdb$",
full.names
>> = TRUE)
>> getratings <- lapply(sitefiles, getDataRatingDepotFiles)
>>
>> Is there any way to replicate the above with fread?
>I don't follow. fread reads the file. 'select' arg can be used to 
>select columns, or you can use setnames() afterwards to rename them. 
>fread doesn't create factors anyway. The numeric columns should be 
>detected automatically but you can pass 'colClasses' manually to fread 
>if you need to read integer data as a numeric type, in the latest 
>version. Or are you asking if fread can read multiple files?
>
>
>>
>> Irucka
>>
>>
>>
>>
>>
>>
>>
>>
>> The comments are really a banner at the start of the file it seems.
So this
>> is all built in to fread already. But the banner in the example is 34
rows,
>> so the default of autostart=30 isn't enough. Try:
>>
>> fread("03217500.exsa.rsb", autostart=40)
>>
>> That should do it in one shot, including detecting the column names.
I've
>> just increased autostart a bit to be within the data block. See
?fread for
>> a detailed description of autostart and the procedure.
>>
>> Btw, if there is more than one table in a single file, then setting
>> autostart to be within each one is how to read each one in. And
provided
>> there is no footer, you can set autostart to be very large, too (with
>> downside of time to seek back from the end to find the column names).
>>
>> Matthew
>>
>>
>>
>> --
>> View this message in context:
http://r.789695.n4.nabble.com/data-table-on-existing-data-
>frame-list-tp4673142p4673201.html
>> Sent from the datatable-help mailing list archive at Nabble.com.
>> _______________________________________________
>> datatable-help mailing list
>> datatable-help at lists.r-forge.r-project.org
>>
https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-h
elp
>>
>
>.
> 


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