Re: Import numbers and dates

*To*: mathgroup at smc.vnet.net*Subject*: [mg30581] Re: [mg30558] Import numbers and dates*From*: "P.J. Hinton" <paulh at wolfram.com>*Date*: Thu, 30 Aug 2001 03:51:27 -0400 (EDT)*Organization*: "Wolfram Research, Inc."*Sender*: owner-wri-mathgroup at wolfram.com

On Wed, 29 Aug 2001, Martin Richter wrote: > I want to import some data which consists 3862 lines, each lines looks like > this: > 07-01-85 101.101897 07-01-85 101.101897 > > So 1. and 3. rows are dates and should be read that way and 2. and 4. rows > are real numbers. I have tried something like this: > data = Import["file.txt", "Table", DateStyle -> European]; There are several problems here: 1) The heuristic that Import[] applies to determine if a field is a date assumes that a forward slash is used as a delimiter, not a minus sign. Your example gets parsed as a subtraction operation. 2) Format specific settings for Import are passed as aggregate options. The correct syntax for specifying the date format would be ConversionOptions -> {"DateStyle" -> "European"} 3) The date uses a two-digit format. The default behavior is to leave dates with two-digit years as strings rather than trying to expand them out to a date with a four-digit year. There is a conversion option called "TwoDigitYearFunction" which enables the user to specify what kind of heuristic should be applied. > Indeed this is easy in Excel but I would like to use Mathematica 4.1. > (I properly getting environmental damage :-) If you are dealing with a data set that cannot be reformatted easily, then it's probably better to write a few lines of Mathematica code that is tailored to your specific problem. Start by writing a function that breaks a date field into its proper elements: parseMyDate[str_String]:= Module[ {stmp, lst}, stmp = StringToStream[str]; lst = ReadList[stmp, {Word, Word, Word}, WordSeparators -> "-"]; Close[stmp]; Return[Flatten[ToExpression /@ lst]] ] parseMyDate[expr_]:= expr Note that this function should probably have some additional validation elements if other, non-date, non-numeric fields are present. We also provide a higher level function that reads in the complete file. importMyTable[fileName_String]:= Map[ parseMyDate, ReadList[ fileName, {Word, Number, Word, Number} ], {2} ] Here is the output for a two-record data set that uses your formatting convention. In[]:= importMyTable["mydata.dat"] Out[]= {{{7, 1, 85}, 101.102, {7, 1, 85}, 101.102}, {{7, 1, 85}, 101.102, {7, 1, 85}, 101.102}} -- P.J. Hinton User Interface Programmer paulh at wolfram.com Wolfram Research, Inc.