importing data

Thanks a million for all help provided!! I can do what I intend to 
using the "for loop". However, I'm still eager to try the list.files 
approach. Here is the error message that I got using Ivan's code:

list_of_dataset <- do.call(read.table, file_names)

Error in do.call(read.table, file_names) : second argument must be a list

Please advise.

Ray

On Sun, Jan 27, 2013 at 10:57 PM, Ivan Calandra 
<ivan.calandra at u-bourgogne.fr <mailto:ivan.calandra at u-bourgogne.fr>> 
wrote:

    Hi Ray!

    I'm insisting with list.files...!

    What about like this (untested)?
    file_names <- list.files(path="C:/.../data", pattern=".dat$",
    full.names=TRUE)
    list_of_dataset <- do.call(read.table, file_names)

    Let me know if this helps!
    Ivan

    -- Ivan CALANDRA Universit? de Bourgogne UMR CNRS/uB 6282
    Biog?osciences 6 Boulevard Gabriel 21000 Dijon, FRANCE
    +33(0)3.80.39.63.06 <tel:%2B33%280%293.80.39.63.06>
    ivan.calandra at u-bourgogne.fr <mailto:ivan.calandra at u-bourgogne.fr>
    http://biogeosciences.u-bourgogne.fr/calandra

    Le 26/01/13 10:03, Ray Cheung a ?crit :

    Thanks for your commands, Ivan and Michael! However, I am still
    not producing the right codes. Would you please help me on
    this? I've written the following codes. Please comment. Thank you
    very much.
    Task: Reading data1.dat to data1000.dat (with missing files) into
    R. Missing files can be omitted in the list.
    ###FUNCTION TO READ FILES
    little_helpful <- function(n) {
    file_name <- paste0("C:/.../data", n, ".dat")
    read.table(file_name)
    }
    ###RETURN AN OBJECT WHICH CHECKS FOR THE EXISTENCE OF FILES
    check  <- function(n) {
    a <- ifelse(file.exists(paste0("C:/.../data", n, ".dat")), 1, 0)
    a
    }
    ###Combining the functions
    IMPORT <- function(n) {
       L <- check(1:n)
       for (i in 1:n) {
          if (L[i] == 1)
          list_of_datasets <- lapply(i, little_helpful) else
    list_of_datasets <- 0
          }
       list_of_datasets
       }
    Thanks for all comments.
    Best Regards,
    Ray

    On Fri, Jan 25, 2013 at 5:48 PM, Ivan Calandra
    <ivan.calandra at u-bourgogne.fr
    <mailto:ivan.calandra at u-bourgogne.fr>> wrote:

        Hi,

        Not sure this is what you need, but what about list.files()?
        It can get you all the files from a given folder, and you
        could then work this list with regular expressions for example.

        HTH,
        Ivan

        --
        Ivan CALANDRA
        Universit? de Bourgogne
        UMR CNRS/uB 6282 Biog?osciences
        6 Boulevard Gabriel
        21000 Dijon, FRANCE
        +33(0)3.80.39.63.06 <tel:%2B33%280%293.80.39.63.06>
        ivan.calandra at u-bourgogne.fr
        <mailto:ivan.calandra at u-bourgogne.fr>
        http://biogeosciences.u-bourgogne.fr/calandra

        Le 25/01/13 10:00, R. Michael Weylandt a ?crit :

            On Fri, Jan 25, 2013 at 6:11 AM, Ray Cheung
            <ray1728 at gmail.com <mailto:ray1728 at gmail.com>> wrote:

                Dear Michael,

                Thanks for your codes. However, lapply does not work
                in my case since I've
                some files missing in the data (say, the file
                data101.dat). Do you have any
                suggestions on this?? Thank you very much.

            You could simply add a test using file.exists() but I'm
            not sure what
            you want to do with the M matrix then -- omit the slice
            (so the others
            are all shifted down one) or fill it entirely with NA's.

            Michael

Dear Ivan,
It works perfectly fine now. I love this code more since I need not 
delete the NULL list myself (and it should be faster, right?). Thank 
you very much for your help!
cheers,
Ray

On Mon, Jan 28, 2013 at 5:32 PM, Ivan Calandra 
<ivan.calandra at u-bourgogne.fr <mailto:ivan.calandra at u-bourgogne.fr>> 
wrote:

    What about this then:
    list_of_datasets <- lapply(file_names, read.table,
    other_args_to_read.table)

    Something that might then be useful is:
    names(list_of_datasets) <- file_names

    Does it do it now?


    Ivan

    --
    Ivan CALANDRA
    Universit? de Bourgogne
    UMR CNRS/uB 6282 Biog?osciences
    6 Boulevard Gabriel
    21000 Dijon, FRANCE
    +33(0)3.80.39.63.06 <tel:%2B33%280%293.80.39.63.06>
    ivan.calandra at u-bourgogne.fr <mailto:ivan.calandra at u-bourgogne.fr>
    http://biogeosciences.u-bourgogne.fr/calandra

    Le 28/01/13 07:34, Ray Cheung a ?crit :

        Thanks a million for all help provided!! I can do what I
        intend to using the "for loop". However, I'm still eager to
        try the list.files approach. Here is the error message that I
        got using Ivan's code:

        > list_of_dataset <- do.call(read.table, file_names)

        Error in do.call(read.table, file_names) : second argument
        must be a list

        Please advise.

        Ray

        On Sun, Jan 27, 2013 at 10:57 PM, Ivan Calandra
        <ivan.calandra at u-bourgogne.fr
        <mailto:ivan.calandra at u-bourgogne.fr>
        <mailto:ivan.calandra at u-bourgogne.fr
        <mailto:ivan.calandra at u-bourgogne.fr>>> wrote:

            Hi Ray!

            I'm insisting with list.files...!

            What about like this (untested)?
            file_names <- list.files(path="C:/.../data", pattern=".dat$",
            full.names=TRUE)
            list_of_dataset <- do.call(read.table, file_names)

            Let me know if this helps!
            Ivan

            -- Ivan CALANDRA Universit? de Bourgogne UMR CNRS/uB 6282
            Biog?osciences 6 Boulevard Gabriel 21000 Dijon, FRANCE
        +33(0)3.80.39.63.06 <tel:%2B33%280%293.80.39.63.06>
        <tel:%2B33%280%293.80.39.63.06>
        ivan.calandra at u-bourgogne.fr
        <mailto:ivan.calandra at u-bourgogne.fr>
        <mailto:ivan.calandra at u-bourgogne.fr
        <mailto:ivan.calandra at u-bourgogne.fr>>

        http://biogeosciences.u-bourgogne.fr/calandra

            Le 26/01/13 10:03, Ray Cheung a ?crit :

                Thanks for your commands, Ivan and Michael! However, I
            am still
                not producing the right codes. Would you please help me on
                this? I've written the following codes. Please
            comment. Thank you
                very much.
                Task: Reading data1.dat to data1000.dat (with missing
            files) into
                R. Missing files can be omitted in the list.
                ###FUNCTION TO READ FILES
                little_helpful <- function(n) {
                file_name <- paste0("C:/.../data", n, ".dat")
                read.table(file_name)
                }
                ###RETURN AN OBJECT WHICH CHECKS FOR THE EXISTENCE OF
            FILES
                check  <- function(n) {
                a <- ifelse(file.exists(paste0("C:/.../data", n,
            ".dat")), 1, 0)
                a
                }
                ###Combining the functions
                IMPORT <- function(n) {
                   L <- check(1:n)
                   for (i in 1:n) {
                      if (L[i] == 1)
                      list_of_datasets <- lapply(i, little_helpful) else
                list_of_datasets <- 0
                      }
                   list_of_datasets
                   }
                Thanks for all comments.
                Best Regards,
                Ray

                On Fri, Jan 25, 2013 at 5:48 PM, Ivan Calandra
                <ivan.calandra at u-bourgogne.fr
            <mailto:ivan.calandra at u-bourgogne.fr>
                <mailto:ivan.calandra at u-bourgogne.fr
            <mailto:ivan.calandra at u-bourgogne.fr>>> wrote:

                    Hi,

                    Not sure this is what you need, but what about
            list.files()?
                    It can get you all the files from a given folder,
            and you
                    could then work this list with regular expressions
            for example.

                    HTH,
                    Ivan

                    --
                    Ivan CALANDRA
                    Universit? de Bourgogne
                    UMR CNRS/uB 6282 Biog?osciences
                    6 Boulevard Gabriel
                    21000 Dijon, FRANCE
            +33(0)3.80.39.63.06 <tel:%2B33%280%293.80.39.63.06>
            <tel:%2B33%280%293.80.39.63.06>
            ivan.calandra at u-bourgogne.fr
            <mailto:ivan.calandra at u-bourgogne.fr>
                    <mailto:ivan.calandra at u-bourgogne.fr
            <mailto:ivan.calandra at u-bourgogne.fr>>

            http://biogeosciences.u-bourgogne.fr/calandra

                    Le 25/01/13 10:00, R. Michael Weylandt a ?crit :

                        On Fri, Jan 25, 2013 at 6:11 AM, Ray Cheung
                        <ray1728 at gmail.com <mailto:ray1728 at gmail.com>
            <mailto:ray1728 at gmail.com <mailto:ray1728 at gmail.com>>> wrote:

                            Dear Michael,

                            Thanks for your codes. However, lapply
            does not work
                            in my case since I've
                            some files missing in the data (say, the file
                            data101.dat). Do you have any
                            suggestions on this?? Thank you very much.

                        You could simply add a test using
            file.exists() but I'm
                        not sure what
                        you want to do with the M matrix then -- omit
            the slice
                        (so the others
                        are all shifted down one) or fill it entirely
            with NA's.

                        Michael