[Numpy-discussion] newbie: attempt at data frame

Vincent Nijs v-nijs at kellogg.northwestern.edu
Thu Dec 28 19:43:42 CST 2006


Sorry for the extra post. There were are few errors in the previous
attachment.

Vincent


On 12/28/06 5:39 PM, "Vincent Nijs" <v-nijs at kellogg.northwestern.edu> wrote:

> Based on Eike's input the dbase class can now also load and dump (simple)
> csv and pickle files. See the tests at the bottom of the file and the
> doc-strings.
> 
> If there is an easy way to read array data + variable names using the csv
> module it would be great if that could be added to cookbook/InputOutput. I
> couldn't figure out how to do it.
> 
> Eike:
> I think I can figure out how to add a plot method. However, if you have some
> more suggestions on how to implement the getAtTime, extract, and set methods
> you mentioned that would be great.
> 
> Vincent
> 
> 
> On 12/28/06 1:40 PM, "Vincent Nijs" <v-nijs at kellogg.northwestern.edu> wrote:
> 
>> Thanks for the input Eike.
>> 
>> I will add load and store methods to Pickle/UnPickle the object. I have got
>> to get the data into the class first however from an ascii file (txt or
>> csv).
>> 
>> I'd like to read the data and variable names directly from a single csv
>> file. I tried this through the python csv module but it would read all data
>> as strings and I couldn't figure out how to easily separate the variable
>> names and the data. I you have any suggestion on how I might do this please
>> let me know.
>> 
>> Unfortunately I don't know what a 'set' method is or would do :) Could you
>> point to an example perhaps.
>> 
>> I like your ideas for extending the class. I'll look into that when I get
>> the basic class working.
>> 
>> Best,
>> 
>> Vincent
>> 
>> 
>> On 12/28/06 12:54 PM, "Eike Welk" <eike.welk at gmx.net> wrote:
>> 
>>> If your main concern is to store scientific data on disk you might
>>> try: 
>>> http://www.pytables.org/moin
>>> 
>>> However, it uses numarray internally and a C library, which you have
>>> to build from source. (You use a Mac right?)
>>> 
>>> 
>>> Concerning your code:
>>> - Your two file solution seems impractical to me. I think you should
>>> just pickle your whole dbase object.
>>> - Maybe you should write 'load' and 'store' methods that create the
>>> temporary file, Pickler and Unpickler objects.
>>> -The __init__ method should then construct the object from a list of
>>> variable names and an array.
>>> -Offcourse you need a set method.
>>> 
>>> more ideas:
>>> - A special variable name 'time'. Then you can implement a
>>> getAtTime( varNameList, timePoint) method with interpolation.
>>> - A 'plot' method that works like matplotlib's plot function.
>>> - An extract(varNameList) method, that returns a new dbase object with
>>> only the selected variables.
>>> - A companion class that can hold several time series at once to
>>> compare different experiments.
>>> 
>>> Finally, post the code to the mailing list. At least I would like to
>>> use such a class :-).
>>> 
>>> Yours
>>> Eike.
>>> 
>>> _______________________________________________
>>> Numpy-discussion mailing list
>>> Numpy-discussion at scipy.org
>>> http://projects.scipy.org/mailman/listinfo/numpy-discussion
>>> 

-- 
Vincent R. Nijs
Assistant Professor of Marketing
Kellogg School of Management, Northwestern University
2001 Sheridan Road, Evanston, IL 60208-2001
Phone: +1-847-491-4574 Fax: +1-847-491-2498
E-mail: v-nijs at kellogg.northwestern.edu
Skype: vincentnijs


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