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Modeling actual data
Posted: Fri Dec 18, 2009 2:46 pm
by PattiCat
I have voluminous amounts of data in SPSS. (tens of thousands of subjects each with hundreds of variables) How can I map those data directly into Vensim without moving it to Excel first? The dataset is too large for Excel.
Also, I've created models with equations based on arbitrary numbers. I'd like to use the actual data so the model matches the data. How can I do this?
PattiCat
Posted: Fri Dec 18, 2009 3:29 pm
by Administrator
Chapter 16 of the user guide is devoted to getting external data into models.
I am unfamiliar with SPSS, but I am sure it can export CVS/TAB that Vensim can import directly.
Tony.
Posted: Sat Dec 19, 2009 11:54 am
by bob@vensim.com
With that quantity of data the most efficient way to transfer it will be to the .dat format file that vensim uses, possibly along with a .cin file which is used for constants or initial conditions. Chapter 16 of the users guide covers using data. If you want to have a subscript for each subject in the data set, and the subjects are numbered, the convention is to create a subscript element with the subject number as in
subject : s12743,s21877...
unless these numbers are sequential it is also usually easiest to create a subscript definition file programmatic ally, and then paste that into Vensim. 10,000 is too many to do at once, so you will need to break it up into about 10 groups of 1000 then combing them as in
sgroup1 : s1,s2
sgroup2: s3,s4
subject : sgroup1,sgroup2
Posted: Tue Dec 22, 2009 7:14 pm
by PattiCat
Thanks for the guidance. I'll llook at Chapter 16. I'll also consider the grouping of subjects as you suggest.
I'd still like to use my actual data in the model ~ any suggestions?:)
Posted: Wed Dec 23, 2009 11:23 am
by bob@vensim.com
Chapter 16 of the User's Guide.