Rank equal intervals between minimum and maximum

* To rank a var1 based on equal distances between min and max value of var1.
* (This code has not been tested when the minimum is negative).
* rlevesque@videotron.ca.

DATA LIST FREE /var1(F8).
BEGIN DATA.
0 15 31 91 
17 24 29 98
57 90 6 7 
100 24 74 21 
END DATA.
LIST.

COMPUTE dummy=1.
AGGREGATE
  /OUTFILE='min_max.SAV'
  /BREAK=dummy
  /var1_min = MIN(var1) /var1_max = MAX(var1).
MATCH FILES /FILE=*
 /TABLE='min_max.SAV'
 /BY dummy.
*Lets say you want to separate values in 8 intervals.
COMPUTE #delta=(var1_max - var1_min)/8.
COMPUTE inter=MIN(TRUNC(var1/#delta)+1,8).
EXECUTE.


*A short technical note:
*The intervals are closed on the left and opened on the right.
*inter=1 when var1 is in the interval [var1_min, var1_min + 1*#delta)
*inter=2 when var1 is in the interval [var1_min+1*delta, var1_min + 2*#delta)
*...
*inter=8 when var1 is in the interval [var1_min+7*delta, var1_min + 8*#delta)
*inter=9 when var1= var1_max.

*The purpose of the last COMPUTE is to force cases with var1=var1_max into the interval 8. In 
*other words inter =8 is for cases in the closed interval [var1_min+7*delta, var1_min + 8*#delta].

*One impecfect method to avoid this adjustment would be to define delta as follows:
COMPUTE #delta=1.000001*(var1_max - var1_min)/8.