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help for ^fill^                                                (STB-43: dm55)
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Generating sequences and patterns of numeric data: an extension to egen
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A common task in Stata is the creation of repeating patterns and linear 
sequences of numeric data. The ^seq^ command of Cox (1997) makes this simple 
to do.  ^fill^ is an extension to ^egen^ for creating sequences. ^fill()^ 
can create ascending or descending lists, including negative numbers and 
complex repeating patterns.


Syntax
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    ^egen^ [type] varname ^= fill(^numlist^)^

^fill()^ follows much the same syntax as many other ^egen^ functions.
The numlist must contain only numeric values.  Alphabetic characters are not
supported.


Options
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There are no options associated with ^fill()^.


Examples
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To create a sequence of numbers, simply "show" ^fill()^ how the sequence
should look.  It must be a linear progression in order to produce the results
you would expect.  Geometric progressions are not understood.

. ^egen i=fill(1 2)^

. ^egen x=fill(-10 -9)^

. ^egen y=fill(1 3 5)^

. ^egen z=fill(1 1 1 2 2 2)^

            i          x          y          z  
 1.         1        -10          1          1  
 2.         2         -9          3          1  
 3.         3         -8          5          1  
 4.         4         -7          7          2  
 5.         5         -6          9          2  
 6.         6         -5         11          2  
 7.         7         -4         13          3  
 8.         8         -3         15          3  
 9.         9         -2         17          3  
10.        10         -1         19          4  
11.        11          0         21          4  
12.        12          1         23          4  
13.        13          2         25          5  
14.        14          3         27          5  
15.        15          4         29          5  
16.        16          5         31          6  
17.        17          6         33          6  
18.        18          7         35          6  
19.        19          8         37          7  
20.        20          9         39          7  

To produce repeating patterns, you must create the pattern definition by
repeating the pattern twice in the numlist.  For example, to produce a
pattern such as 1, 3, 2, 4, 1, 3, 2, 4 ... issue commands like

. ^egen j=fill(1 3 2 4 1 3 2 4)^

. ^egen k=fill(-2 -1 0 1 2 -2 -1 0 1 2)^

. ^egen l=fill(1 1 2 2 1 1 2 2)^

. ^egen m=fill(0 0 1 0 0 1)^

            j          k          l          m  
 1.         1         -2          1          0  
 2.         3         -1          1          0  
 3.         2          0          2          1  
 4.         4          1          2          0  
 5.         1          2          1          0  
 6.         3         -2          1          1  
 7.         2         -1          2          0  
 8.         4          0          2          0  
 9.         1          1          1          1  
10.         3          2          1          0  
11.         2         -2          2          0  
12.         4         -1          2          1  
13.         1          0          1          0  
14.         3          1          1          0  
15.         2          2          2          1  
16.         4         -2          2          0  
17.         1         -1          1          0  
18.         3          0          1          1  
19.         2          1          2          0  
20.         4          2          2          0  

This is not a command one will likely use everyday, but in many circumstances
^fill()^ should make the generation of repeating sequences and patterns of
numbers quite simple.  In many cases, the ^fill()^ extension can be used
in place of a ^generate^ command and complex expression using ^_n^ or
^_N^.


Author
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       R. Mark Esman
       Stata Corporation
       Fax:  409-696-4601 
       mesman@@stata.com


Reference
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Cox, N. J. 1997. dm44: Sequences of integers. Stata Technical Bulletin 37: 2-4.


Also see
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    STB:  STB-43 dm55