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TSV files as a list of list of lists?

  • To: mathgroup at
  • Subject: [mg101150] TSV files as a list of list of lists?
  • From: Dan-Erik Lindberg < at>
  • Date: Thu, 25 Jun 2009 07:13:50 -0400 (EDT)

I am loading a few GPS data files as TSV (tab separated). What I would like to do is make the loading of files a bit more dynamic, so I make a list of the file contents. But since the file contents is a list in itself, I get in trouble when I want to manipulate the data. It just takes too long.

First, here is how I do it for one file only:

GPS1 = Import["F:\\Documents\\Jobb\\SLU\\xyuvw\\GPS.txt", "TSV"]
(* Remove column-headers *)
GPS1 = Drop[GPS1, 1] 
(* Make sure row 1 of column 2 or 3 doesn't contain spaces so \
they can be interpreted as numbers (I use swedish RT90 \
grid which gives coordinates in meters). *)
If[Head[GPS1[[1, 2]]] == String, 
  GPS1[[All, 2]] = 
   ToExpression[StringReplace[GPS1[[All, 2]], " " -> ""]]];
If[Head[GPS1[[1, 3]]] == String, 
  GPS1[[All, 3]] = 
   ToExpression[StringReplace[GPS1[[All, 3]], " " -> ""]]];
(* Sort the GPS data (first column is time) *)

Now, what I would like to do; make an array of file contents (actually a list):

GPS[1] = Import["F:\\Documents\\Jobb\\SLU\\xyuvw\\GPS.txt","TSV"];
Do[GPS[1] = ReplacePart[GPS[1], {i,2} -> \
ToExpression[StringReplace[GPS1[[All, 2]], " " -> ""]]], {i, 1, \

This second part takes a very long time to do, because ReplacePart[] has to work through every line one at a time rather than using [All, x] as I do in the first example. 

Is there any way of doing this faster?

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