R help - Nov 2014 - 1. What function to use to read all the files in a directory to a vector in R code? 2. What function to use to coerce character string into numeric?

Hi,
I have 2 queries:
1. What function to use to read all the files in a directory to a vector in R
code?
2. What function to use to coerce character string into numeric?
As a help to others, I figured out to use setwd("C:/....") to set
working directory!
Aditya
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1. There is no built-in function to do that, but it can be done if you learn the
basics of R [1]. For one thing, there is no assurance that all files in a
directory will fit into vectors.. Most data fit better into data frames, and
some data like XML need to be stored in lists of lists. So your first task is to
work this out and use the str function to make sure you understand how your data
for one file looks when imported into R variables.

Once you figure out how your files can be read in (perhaps with read.csv or
read.table?) then you can use list.files to get a vector of filenames, and
lapply to create a list of contents of files. You may need to re-read the
discussions of lists and indexing in [1] again to see how to get the pieces out
of the list. If all your files actually do have the same data frame structure,
then you might find it useful to merge the list into a single data frame.
Something like:

fnames <- list.files( pattern="\\.csv$" )
dtalist <- lapply(fnames,function(fn){read.csv(fn,stringsAsFactors=FALSE)})
alldta <- do.call(rbind,dtalist)

2. Read help file ?numeric.

You should also read the Posting Guide, which among other advice mentions that
you should post using plain text format on this list rather than HTML (since we
don't see what you see if you use the latter).

[1] Introduction to R, supplied with the software.
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DCN:<jdnewmil at dcn.davis.ca.us>        Basics: ##.#.       ##.#.  Live
Go...
                                      Live:   OO#.. Dead: OO#..  Playing
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Sent from my phone. Please excuse my brevity.

On November 10, 2014 5:12:10 AM PST, Aditya Singh <aps6dl at yahoo.com>
wrote:
>Hi,
>I have 2 queries:
>1. What function to use to read all the files in a directory to a
>vector in R code?
>2. What function to use to coerce character string into numeric?
>As a help to others, I figured out to use setwd("C:/....") to set
>working directory!
>Aditya
>	[[alternative HTML version deleted]]
>
>______________________________________________
>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.

On Mon, Nov 10, 2014 at 7:12 AM, Aditya Singh <aps6dl at yahoo.com> wrote:
> Hi,
> I have 2 queries:
> 1. What function to use to read all the files in a directory to a vector
> in R code?
> 2. What function to use to coerce character string into numeric?
> As a help to others, I figured out to use setwd("C:/....") to set
working
> directory!
> Aditya
>
?First, please don't post in HTML. It is contrary to forum policy. Thanks.

Answer 1: you can get a list of the names of all the files using the
list.files() function. Do a ?list.files for more information.

Answer 2: If I understand your question correctly, then I'd use
as.numeric() .

Suggestion 1: Get & read a good book on R programming. These were very
basic questions. I'd strongly suggest "Advanced R" by Hadley
Wickham. You
can order if Amazon.com, or read it (for free!) here:
http://adv-r.had.co.nz/
?

?Another good one is "The Art of R Programming" by Norman Matloff.
This
later one is what I used, but that's mainly because Hadley's book
hadn't
been written (or maybe published) when I was first learning R. ?

?Suggestion 2: If you haven't already, I would strongly recommend getting
&
installing RStudio. It is free (as in beer, which is a curious phrase
because beer isn't usually free). http://www.rstudio.com ?

-- 
The temperature of the aqueous content of an unremittingly ogled
culinary vessel will not achieve 100 degrees on the Celsius scale.

Maranatha! <><
John McKown

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