Re: Export, Import, Convert Types Again?
- To: mathgroup at smc.vnet.net
- Subject: [mg57220] Re: Export, Import, Convert Types Again?
- From: Gareth Russell <gjr2008 at columbia.edu>
- Date: Sat, 21 May 2005 02:39:37 -0400 (EDT)
- Organization: Columbia University
- References: <d6k9ev$10q$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Lee,
Usually it suffices to map ToExpression[] over the data you re-imported
-- it should recognize the lists as lists, and so on.
What you are experiencing is not a bug -- you say yourself that you
want to view the exported data in a text editor, so you export using a
function which drops all the Mathematica 'baggage' such as heads.
Gareth
On 2005-05-20 05:08:47 -0400, Lee Newman <leenewm at umich.edu> said:
> 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