* How can I compare (superimpose) 2 histogram.

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* First method.
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* Answer posted to newsgroup by Raynald Levesque on 2003/02/13.

GET FILE='c:\\program files\\spss\\employee data.sav'.
COMPUTE beg=TRUNC(salbegin/5000).
COMPUTE sal=TRUNC(salary/5000).
SORT CASES BY beg.
AGGREGATE OUTFILE='c:\\temp\\beg.sav'
	/PRESORTED
	/BREAK=beg
	/nbeg=n.
SORT CASES BY sal.
AGGREGATE OUTFILE=*
	/PRESORTED
	/BREAK=sal
	/nsal=n.

MATCH FILES FILE=*
	/RENAME=(sal=beg)
	/FILE='c:\\temp\\beg.sav'
	/BY=beg.

GRAPH
  /LINE(MULTIPLE)= VALUE( nbeg nsal ) BY beg .


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* Second Method.
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Date:         Fri, 23 Jun 2000 20:38:37 -0400 
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU> 
From:         Raynald Levesque <rlevesque@VIDEOTRON.CA> 
Subject:      Re: superimpsed histograms 

Hi Arthur!   This is a possible solution:   

*Define dummy data file for illustration purposes.   
NEW file. 
SET SEED=975316421. 
INPUT PROGRAM. 
- LOOP id=1 TO 50.  
-   COMPUTE income=RV.NORMAL(35,5).  
-   COMPUTE group=UNIFORM(1)>.5.  
-   END CASE. 
- END LOOP. 
- END FILE. 
END INPUT PROGRAM. 
EXECUTE. 
SAVE OUTFILE='temp.sav'.     
GRAPH  /HISTOGRAM=income . 

* look at the histogram and note the smallest value and the range of each bin. 
* in this case the smallest mid point of a bin is 18,000 and the range is 2000.   
* Recode the income values as follows. 

LOOP cnt=18 TO 46 BY 2. 
- IF RANGE(income,cnt-1,cnt+0.99999) income1=cnt. 
END LOOP. 
EXECUTE.   
GRAPH   
  /BAR(GROUPED)=COUNT BY income1 BY group   
  /MISSING=REPORT.