[R] Argh! Trouble using string data read from a file
Ted Byers
r.ted.byers at gmail.com
Thu Oct 16 02:42:42 CEST 2008
Thanks Jim,
I hadn't seen the distinction between the commandline in RGui and what
happens within my code.
I have, however seen other differences I don't understand. For
example, looking at the documentation for RScript, I see:
Rscript [options] [-e expression] file [args]
And the example:
Rscript -e 'date()' -e 'format(Sys.time(), "%a %b %d %X %Y")'
So I tried it (Windows XP; R2.7.2), and this is what I got with just
copy directly from the documentation and pasting into the Windows
commandline window:
C:\>Rscript -e 'date()' -e 'format(Sys.time(), "%a %b %d %X %Y")'
[1] "date()"
C:\>Rscript -e 'format(Sys.time(), "%a %b %d %X %Y")'
C:\>
But within RGui, I get:
> date();format(Sys.time(), "%a %b %d %X %Y")
[1] "Wed Oct 15 20:36:57 2008"
[1] "Wed Oct 15 8:36:57 PM 2008"
>
Thanks again
Ted
On Wed, Oct 15, 2008 at 8:09 PM, jim holtman <jholtman at gmail.com> wrote:
> You have to explicitly 'print' the value of x in the loop: print(x)
>
> 'x' by itself is just it value. At the command line, typing an
> objects name is equivalent to printing that object, but it only
> happens at the command line. If you want a value printed, the 'print'
> it. Also works at the command line if you want to use it there also.
>
> On Wed, Oct 15, 2008 at 5:36 PM, Ted Byers <r.ted.byers at gmail.com> wrote:
>> Actually, I'd tried single brackets first. Here is what I got:
>>
>>> for (i in 1:length(V4) ) { x = read.csv(V4[i], header = FALSE, na.strings="");x }
>> Error in read.table(file = file, header = header, sep = sep, quote = quote, :
>> 'file' must be a character string or connection
>>>
>>
>>
>> the advice to use as.character worked, in that progress has been made.
>>
>> Can you guys explain the following output, though?
>>
>>> setwd("K:\\MerchantData\\RiskModel\\AutomatedRiskModel")
>>> for (i in 1:length(V4) ) { x = read.csv(as.character(V4[[i]]), header = FALSE, na.strings="");x }
>>> x
>> V1
>> 1 0
>>> x = read.csv(as.character(V4[[1]]), header = FALSE, na.strings="");x
>> V1
>> 1 0
>> 2 0
>> 3 21
>> 4 0
>> 5 1
>> 6 7
>> 7 51
>> 8 20
>> 9 3
>> 10 5
>> 11 6
>> 12 8
>> 13 2
>> 14 0
>> 15 2
>> 16 4
>> 17 23
>>
>> Clearly, if I hand write a line to read the data, getting the file
>> name from V4 (in this case V4[[1]]), I get the data into 'x', which I
>> can then display. I only displayed the first few as some of these
>> files will have thousands of values.
>>
>> But what puzzles me is that I saw virtually no output from my loop. I
>> thought what would happen (with the x after the ';') is that the
>> contents of each file would be displayed after it is read and before
>> the first is read. And after the loop finishes, there is nothing in
>> x. I don't see why the contents of x would disappear after the loop,
>> unless R has scoping restrictions as stringent as, say, C++ (e.g. a
>> variable declared inside a loop is not visible outside the loop). But
>> that would beg the question as to how to declare a variable before it
>> is first used.
>>
>> This doesn't bode well for me, or perhaps my ability to learn a new
>> trick at my age, when such a simple loop should give me such trouble.
>> :-(
>>
>> Getting more grey hair by the minute. :-(
>>
>> Thanks
>>
>> ted
>>
>> On Wed, Oct 15, 2008 at 5:12 PM, Rolf Turner <r.turner at auckland.ac.nz> wrote:
>>>
>>> On 16/10/2008, at 10:03 AM, jim holtman wrote:
>>>
>>>> try putting as.character in the call:
>>>>
>>>> x = read.csv(as.character(V4[[i]]), header = FALSE
>>>
>>> No. This won't help. V4 is a column of the data frame optdata,
>>> and hence is a vector. Not a list! Use single brackets --- V4[i] ---
>>> and all will be well.
>>>
>>> cheers,
>>>
>>> Rolf
>>>>
>>>> On Wed, Oct 15, 2008 at 4:46 PM, Ted Byers <r.ted.byers at gmail.com> wrote:
>>>>>
>>>>> Here is what I tried:
>>>>>
>>>>> optdata =
>>>>> read.csv("K:\\MerchantData\\RiskModel\\AutomatedRiskModel\\soptions.dat",
>>>>> header = FALSE, na.strings="")
>>>>> optdata
>>>>> attach(optdata)
>>>>> for (i in 1:length(V4) ) { x = read.csv(V4[[i]], header = FALSE,
>>>>> na.strings="");x }
>>>>>
>>>>> And here is the outcome (just a few of the 60 records successfully
>>>>> read):
>>>>>>
>>>>>> optdata =
>>>>>>
>>>>>> read.csv("K:\\MerchantData\\RiskModel\\AutomatedRiskModel\\soptions.dat",
>>>>>> header = FALSE, na.strings="")
>>>>>> optdata
>>>>>
>>>>> V1 V2 V3 V4
>>>>> 1 251 2008 18 Plus_Shipping.2008.18.dat
>>>>> 2 251 2008 19 Plus_Shipping.2008.19.dat
>>>>> 3 251 2008 20 Plus_Shipping.2008.20.dat
>>>>> 4 251 2008 22 Plus_Shipping.2008.22.dat
>>>>> 5 251 2008 23 Plus_Shipping.2008.23.dat
>>>>> 6 251 2008 24 Plus_Shipping.2008.24.dat
>>>>>
>>>>> I can see the data has been correctly read. But for some reason that
>>>>> isn't
>>>>> clear, read.csv doesn't like the data in the last column.
>>>>>
>>>>>> attach(optdata)
>>>>>> for (i in 1:length(V4) ) { x = read.csv(V4[[i]], header = FALSE,
>>>>>> na.strings="");x }
>>>>>
>>>>> Error in read.table(file = file, header = header, sep = sep, quote =
>>>>> quote,
>>>>> :
>>>>> 'file' must be a character string or connection
>>>>>>
>>>>>> V4[[1]]
>>>>>
>>>>> [1] Plus_Shipping.2008.18.dat
>>>>> 60 Levels: Easyway.2008.17.dat Easyway.2008.18.dat Easyway.2008.19.dat
>>>>> Easyway.2008.20.dat ... Secured_Pay.2008.31.dat
>>>>>
>>>>>>
>>>>>
>>>>> The last column is comprised of valid Windows filenames (and no
>>>>> whitespace,
>>>>> so as not to confuse things).
>>>>>
>>>>> I see in the docuentation "`[[...]]' is the operator used to select a
>>>>> single
>>>>> element, whereas `[...]' is a general subscripting operator.", so I
>>>>> assume
>>>>> V4[[i]] is the correct way to get the ith value from V4. So why does
>>>>> read.csv complain that "'file' must be a character string or connection"?
>>>>> It seems obvious that the value in V4[[i]i] is a string. V4[[1]] does
>>>>> give
>>>>> me the right value, although that is followed by output I didn't ask for.
>>>>>
>>>>> In the loop above, I was going to replace the output obtained by 'x' with
>>>>> output from fitdistr(x,"exponential"), but I can't proceed with that
>>>>> until I
>>>>> can get the data in these files read.
>>>>>
>>>>> What have I missed?
>>>>>
>>>>> Thanks
>>>>>
>>>>> Ted
>>>>> --
>>>>> View this message in context:
>>>>> http://www.nabble.com/Argh%21--Trouble-using-string-data-read-from-a-file-tp20002064p20002064.html
>>>>> Sent from the R help mailing list archive at Nabble.com.
>>>>>
>>>>> ______________________________________________
>>>>> 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.
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Jim Holtman
>>>> Cincinnati, OH
>>>> +1 513 646 9390
>>>>
>>>> What is the problem that you are trying to solve?
>>>>
>>>> ______________________________________________
>>>> 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.
>>>
>>>
>>> ######################################################################
>>> Attention:This e-mail message is privileged and confidential. If you are not
>>> theintended recipient please delete the message and notify the sender.Any
>>> views or opinions presented are solely those of the author.
>>>
>>> This e-mail has been scanned and cleared by
>>> MailMarshalwww.marshalsoftware.com
>>> ######################################################################
>>>
>>
>> ______________________________________________
>> 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.
>>
>
>
>
> --
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
>
> What is the problem that you are trying to solve?
>
More information about the R-help
mailing list