Re: [R] Argh! Trouble using string data read from a file

Wed, 15 Oct 2008 15:08:31 -0700 

[[ ]] works on vectors!


letters[[3]]

[1] "c"
See help("[["). But strictly V4 is a factor and hence not a vector: [[ ]] also works on factors. 

On Thu, 16 Oct 2008, Rolf Turner 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 <[EMAIL PROTECTED]> 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
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--
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

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--
Brian D. Ripley,                  [EMAIL PROTECTED]
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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