Stata Class Notes
Reshaping Datasets


1.0 Stata commands in this unit

. reshape

2.0 Demonstration and Explanation

There are two major varities of data files; those that are long and those that are wide. An example of a wide file is shown in the table below.

Example Wide File

 id       grp     lrn95     lrn96     lrn97
  1         1         7        12        16 
  2         1        13        14        15 
  3         2        15        14        20 
  4         2        21        27        24 
  5         3         9         9        12 
  6         3        16        17        18 

We would like to change this file to the long format that looks like this:

Example Long File

 id       year       grp       lrn 
  1         95         1         7  
  1         96         1        12  
  1         97         1        16  
  2         95         1        13  
  2         96         1        14  
  2         97         1        15  
  3         95         2        15  
  3         96         2        14  
  3         97         2        20  
  4         95         2        21  
  4         96         2        27  
  4         97         2        24  
  5         95         3         9  
  5         96         3         9  
  5         97         3        12  
  6         95         3        16  
  6         96         3        17  
  6         97         3        18  

2.1 Wide to long example

use http://www.ats.ucla.edu/stat/stata/notes/wide, clear
describe
list
reshape long lrn, i(id) j(year)
describe
list
table year, contents(n lrn mean lrn sd lrn)

2.2 Back to wide again

. reshape wide
describe
list
reshape long
describe
list

2.3 Split-plot factorial example

. use spf2, clear
describe
list
reshape long y, i(s) j(b)
describe
list
anova y a / s|a b a*b, repeated(b)

3.0 Try the commands on your own

. use wide,clear
describe
list
reshape long lrn, i(id) j(year)
describe
list

4.0 For More Information

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