Suppose I have a number of .gpx files (these contain GPX waypoint data from a Garmin eTrex). I want to load them into R with different names and manipulate them.

I can read one file thus:

gpx.raw <- readGPS(i = "gpx", f = "file1_w_12_f_ddf.gpx", type="w")

Suppose I want to read a number of them into memory. I could try a for loop:

files <- list.files(".",pattern = "*.gpx")
for(x in files){

    #Create new file name
    temp <- strsplit(x,"_",fixed=TRUE)
    visit.id <- sapply(temp,FUN=function(x){paste(x[1],x[4],substr(x[5],1,3),sep="_")})

    #read file with new filename
    assign(visit.id, readGPS(i = "gpx", f = x, type="w"))

Running above program yields following error:

Error in read.table(con <- textConnection(gpsdata), fill = TRUE, ...) : no lines available in input In addition: Warning message: running command 'C:\PROGRA~2\GPSBabel\gpsbabel.exe -w -i gpx -f file1_w_12_f_ddf.gpx -o tabsep -F -' had status 1

Note that I was able to read this file on its own, so it would seem it has nothing to do with the file itself but with running readGPS in a loop.

In general I still find it very confusing how R treats variables like x above. I am not sure how to modify the argument to readGPS from the stand alone instance f = "file1_w_12_f_ddf.gpx": Should it be x, or f = x, or f = "x", or what? Or maybe the problem is in the call to GPSBabel...

I include a sample file below so you can copy it to text editor, and save as .gpx. twice with different names and try yourself.

<?xml version="1.0" encoding="UTF-8"?>
 creator="GPSBabel - http://www.gpsbabel.org"
 xsi:schemaLocation="http://www.topografix.com/GPX/1/0 http://www.topografix.com/GPX/1/0/gpx.xsd">
 <bounds minlat="18.149888897" minlon="-96.747799935" maxlat="50.982883293" maxlon="121.640266674"/>
<wpt lat="38.855549991" lon="-94.799016668">
 <wpt lat="50.982883293" lon="-1.463899976">
 <wpt lat="25.061783362" lon="121.640266674">

closed as not constructive by Mapperz Jun 19 '11 at 2:38

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  • it is generally discouraged to cross-post. Since you have already an excepted answer on SO, I have flagged this post to be closed. Another reasonable solution would be to simply close the question yourself. – Andy W Jun 19 '11 at 2:08
  • Thanks Andy - The dup stackoverflow.com/questions/6397523/read-multiple-gpx-files is outside the GISse domain - Though due to "No eligible question found at that url." Can close with other methods – Mapperz Jun 19 '11 at 2:38
  • @Andy W - Not sure what is wrong with cross-posting. Two different audiences with different expertise. Unless we are going to get territorial. That said, I want to remove the question since it was really just a problem with file names. How do I do that? – Fred Jun 19 '11 at 15:17

I can't say why it is not working with the readGPS function in the maptools package, but I was able to loop through the files reading in the data using the readOGR function in the rgdal package.

setwd("C:\\Documents and Settings\\Owner\\Desktop\\R_test")

#I just saved my text files in the above directory
myfiles <- list.files()

#this works, note track_points on layer name does not work!
gpx.raw <- readOGR(dsn = myfiles[1], layer="waypoints")

#now making function
for (i in 1:3) {
temp.gpx <- readOGR(dsn = myfiles[i], layer="waypoints")
  • Thanks. Actually it works, but I found out that GPSbabel does not like filenames with empty spaces. The name of my first file was something like "file1 w 12_f_ddf.gpx" so it escaped right there. – Fred Jun 18 '11 at 23:55
  • @Fred , you should either post that as an answer and accept it, or just accept this answer since your problem is solved. – Andy W Jun 19 '11 at 0:35
  • Was going to post it as answer but I cannot answer my own q within 24 hours... – Fred Jun 19 '11 at 15:12

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