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st: RE: A strange data problem

From   "David Harrison" <[email protected]>
To   <[email protected]>
Subject   st: RE: A strange data problem
Date   Mon, 17 Jan 2005 08:56:30 -0000

It is clear from -describe- that you have successfully transferred UPC as a double. However, you have generated the new variable UPC1 as a float - losing some of the precision of UPC. To create a variable UPC1 that is identical to UPC, you need:

gen double UPC1=UPC

See the manuals for [U] 16.10 Precision and problems therein.

[email protected]

-----Original Message-----
From: Maoyong Fan [mailto:[email protected]]
Sent: 16 January 2005 06:16
To: statalist
Subject: st: A strange data problem

Dear Stata User,

        I met a strange problem in dealing with my scanner data.  I use stata transfer to transger the original data to dta files.  One of my variables is UPC whose storage type is double.  I found that when I generate a new variable equal to UPC, the new variable is totally different from UPC.

Like this:
gen UPC1 = UPC
gen diff = UPC1 - UPC

    Variable |       Obs        Mean    Std. Dev.       Min        Max
         UPC |   1780770    3.76e+10    1.96e+11   1.00e+10   2.72e+12
        UPC1 |   1780770    3.76e+10    1.96e+11   1.00e+10   2.72e+12
        diff |   1780770    144.9445    4290.722    -105114     116086

. des

Contains data from D:\temp\dairyHH1.dta
  obs:     1,780,770                         
 vars:             3                          18 Jun 2003 13:27
 size:    35,615,400 (66.0% of memory free)
              storage  display     value
variable name   type   format      label      variable label
UPC             double %15.0g                 UPC -
UPC1            float  %9.0g                 
diff            float  %9.0g                 
Sorted by: 
     Note:  dataset has changed since last saved

Anyone know what's wrong with this?    

Warm regards,

Maoyong Fan

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