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Re: Export, Import, Convert Types Again?

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  • Subject: [mg57214] Re: [mg57193] Export, Import, Convert Types Again?
  • From: Clifford Martin <camartin at>
  • Date: Sat, 21 May 2005 02:39:27 -0400 (EDT)
  • Sender: owner-wri-mathgroup at


I do something similar. I import data from Excel into
Mathematica then create my functions, etc. inside
Mathematica.  Then I save the whole session using
DumpSave. This maintains my data, my functions, etc.
If I want to view stuff with outside programs I Export
similarly to what you did but don't try to reimport
that data. I continue to use my DumpSave file. Works
fairly well.


--- Lee Newman <leenewm at> wrote:
> 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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