Bootstrap the mean and median

SET PRINTBACK ON MPRINT ON .
* Bootstrap the mean and the median.
* Author: David Marso.

* Raynald's note: 474 is the number of cases in the file. It is possible to let the syntax 
automatically determine this number (see bcnon.sps for instance).

GET FILE='C:\\Program Files\\SPSS\\Employee data.sav'.
BOOTMED NSAMP=1000 NSIZE = 474 BOOTVAR=SALARY OUTFILE=BOOTME .
**GET THE BOOT STRAP FILE AND SMILE *.
get file "BOOTME" .


DEFINE BOOTMED ( NSAMP !TOKENS(1)
/ NSIZE !TOKENS(1) 
/ BOOTVAR !TOKENS(1) 
/ OUTFILE !TOKENS(1) ) .
* STUFF IT ALL ***SORTED*** INTO ONE CASE * .
sort cases by !BOOTVAR .
vector data (!NSIZE).
compute data($casenum)=!BOOTVAR .
compute nobreak=1.
aggregate outfile *
/ break nobreak
/ data1 to !CONCAT(data,!NSIZE) = max(data1 to !CONCAT(data,!NSIZE)). 

* DO ON THE FLY RANDOMIZATION AND STAT CALCULATION * .

vector data=data1 to !CONCAT(data,!NSIZE) .
vector tmp (!NSIZE).

loop #P=1 to !NSAMP.
* INITIALIZE A STORAGE ARRAY FOR EACH ITERATION * .
loop #=1 to !NSIZE .
compute tmp(#)=0.
end loop.

* INCREMENT STORAGE EACH TIME A CASE IS SAMPLED * .
loop #I=1 to !NSIZE .
compute ID=trunc(uni(!NSIZE )+1).
compute tmp(ID)=TMP(ID)+1.
end loop.

**** IN THIS EXAMPLE I CREATE THE MEDIAN AND MEAN**** .
**** YOU MAY WISH TO USE A DIFFERENT FUNCTION ****.
**** IN WHICH CASE PLUG AWAY!!! ****

* CALCULATE THE CASE COUNT CONTAINING THE MEDIAN * .
compute tot=0.
compute crit=!NSIZE / 2.

* LOOP UNTIL YOU FIND THE CRITICAL CASE * .
loop #=1 to !NSIZE .
compute tot=tot + tmp(#).
end loop if tot >=crit .

* CALCULATE THE MEDIAN * .
do if mod(!NSIZE,2)=0 .
compute median=(data(#) + data(#-1))/2.
else.
compute median=data(#).
end if .

*** COMPUTE MEAN USING SAME SAMPLE *** .
compute MEAN=0 .
loop # = 1 to !NSIZE .
compute MEAN=MEAN + data(#) * tmp(#) .
end loop.
COMPUTE MEAN=MEAN / !NSIZE .


* DUMP THE MEAN and MEDIAN TO The OUTFILE * .
xsave outfile !QUOTE(!OUTFILE) / keep median MEAN .
* DO IT AGAIN AND AGAIN AND AGAIN .... * .
end loop .
execute .

!ENDDEFINE .