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MathGroup Archive 2005

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Re: Export, Import, Convert Types Again?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg57237] Re: [mg57193] Export, Import, Convert Types Again?
  • From: "Tomas Garza Hernandez" <tgarza10 at msn.com>
  • Date: Sat, 21 May 2005 02:40:45 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

If you are using your imported data only within Mathematica (except, of 
course, when you are through with the problem), then use ">>" (called "Put") 
to save in internal format, and  "<<" (or "Get") to retrieve into your 
notebook. This will preserve your data exactly as used in the notebook.

Tomas Garza
Mexico City

>From: Lee Newman <leenewm at umich.edu>
To: mathgroup at smc.vnet.net
>Subject: [mg57237] [mg57193] Export, Import, Convert Types Again?
>Date: Fri, 20 May 2005 04:43:32 -0400 (EDT)
>
>Q: What is the (best) way to save a big expression of data to be used
>later in the same notebook without having to do type conversion processing?
>
>Situation:
>
>1) I have a notebook that imports data from various Excel spreadsheets
>and converts the data to the desired types.  When complete, I "save" the
>expression containing the data using Export, i.e,
>Export["featureDB.tsv", "TSV"].  I do this so I don't have to re-process
>the data everytime I do analysis on it in this notebook.
>
>2) When I open the noteobook again, I import the data using the
>statement:  featureDB = Import["featureDB.tsv"]
>
>Problem:
>Many of type conversions that I took the time to process are lost.
>Using Head /@ featureDB[[1]]  before and after the export/re-import, the
>types are as follows:
>
>Before:  {Integer, Integer, List, List, List, Integer, List, List,
>Symbol, List}
>After   : {Integer, Integer, String, String, String, Integer, String,
>String, String, String}
>
>So it seems that lists become Strings as  Symbols (e.g. True, False,
>Null).  I use Export so I can view the data outside Mathematica using a 
>text
>editor -- should I use Save instead?  Is there another Export format
>that will preserve mathematica expressions like lists upon Import?
>
>Thanks,
>Lee
>
>
>
>



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