[R] trouble with exporting a data.frame with " (quotation mark) in some columns into a tab delimited file, then importing the file

[Patrick Giraudoux]

Dear listers, here in plain text,

I encountered an issue with a CSV file that was imported correctly but 
could not be re-imported correctly after being written with R. This is 
probably because geographical coordinates were imported  as character in 
degrees, minutes and seconds (DMS), which includes " (quotation mark) 
for the seconds.

Below a reproducible example:

db <- structure(list(lon = c(6.228561, 6.22532, 6.2260499999999999, 
6.2267789999999996, 6.2224659999999998, 6.2209430000000001), latdms = 
c("47°12'28.36\"N", "47°12'33.46\"N", "47°12'28.37\"N", 
"47°12'27.48\"N", "47°12'31.31\"N", "47°12'33.15\"N"), londms = 
c("6°13'42.82\"E", "6°13'31.15\"E", "6°13'33.78\"E", "6°13'36.40\"E", 
"6°13'20.88\"E", "6°13'15.39\"E"), fusutmn = c(32L, 32L, 32L, 32L, 32L, 
32L)), row.names = c(NA, 6L), class = "data.frame") > db lon latdms 
londms fusutmn 1 6.228561 47°12'28.36"N 6°13'42.82"E 32 2 6.225320 
47°12'33.46"N 6°13'31.15"E 32 3 6.226050 47°12'28.37"N 6°13'33.78"E 32 4 
6.226779 47°12'27.48"N 6°13'36.40"E 32 5 6.222466 47°12'31.31"N 
6°13'20.88"E 32 6 6.220943 47°12'33.15"N 6°13'15.39"E 32
write.table(db, file = "db.txt", row.names = FALSE, quote = FALSE, sep = 
"\t") db_import<-read.delim("db.txt") > db_import lon latdms londms 
fusutmn 1 6.228561 47°12'28.36N\t6°13'42.82E 32 NA 2 6.225320 
47°12'33.46N\t6°13'31.15E 32 NA 3 6.226050 47°12'28.37N\t6°13'33.78E 32 
NA 4 6.226779 47°12'27.48N\t6°13'36.40E 32 NA 5 6.222466 
47°12'31.31N\t6°13'20.88E 32 NA 6 6.220943 47°12'33.15N\t6°13'15.39E 32 NA

As you can see it, latdms and londms are now collapsed and all the 
columns on the right  have shifted to the left. I get the same issue 
with ; as a separator.

I could not find a workaround...

Any hint appreciated,

Patrick