Export, Import, Convert Types Again?

*To*: mathgroup at smc.vnet.net*Subject*: [mg57193] Export, Import, Convert Types Again?*From*: Lee Newman <leenewm at umich.edu>*Date*: Fri, 20 May 2005 04:43:32 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

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