Macros Are Just String Parsers!

Subject:Re: I'm stuck
Date:1997/10/02
Author:David Mark Marso <marso@spss.com>

Martin Lee wrote:

Using V7.5 win, I'm trying to produce a routine that will go thru a dataset that has numeric variables named in the style a1000,a1001, a1002... , take five consecutive vars, run some syntax with count and do if to produce a new var, and then move on, skipping two vars, repeat the first exercise, all up 32 times.

I've tried to use a macro - but I don't have an "SPSS Macros for Dummys" book: my best effort is:
                 
> *Macro for counting dmft in DMDS p15, and p18 datasets.
> 1 DEFINE dmftmac  (c1start = !TOKENS(1)
> 2  /c1end = !TOKENS(1)).
> 3 !DO !idx = c1start !TO c1end !BY 7.
> 4  !LET !a = !CONCAT(a,!idx).
> 5  !LET !b = !CONCAT(a,!idx + 4).
> 6  count #(!idx)= !a to !b (1 thru 5).
>    do if (#(!idx) gt 0).
>    compute t(!idx)=1.
>    else.
>    if (#(!idx) eq 0)t(!idx)=0.
>    end if.
>  !DOEND.
> !ENDDEFINE.
>
> dmftmac 1064 1281 .
> exec.
>
> Unfortunately it doesn't like the addition in line 5 (linenums added)and says addition isn't implemented, which is a pity as it's one of the few things I can do! I should have stuck to filling teeth.

Is the answer out there?

If it is I'd be be really grateful.

Martin Lee
Public Health Dentist
Healthlink South
Christchurch, New Zealand
leem1@hsl.co.nz



* No need for a macro here *
* Here is an untested but methodologically correct program using plain old syntax.

Vector vars=a1064 to a1288.
Vector t(32).

loop #=1 to 224 step 7.
do repeat new=XX1 XX2 XX3 XX4 XX5 / J=0 to 4.
compute new=vars(# + J).
end repeat.

count #temp=XX1 to XX5 (1 thru 5).
compute t((#-1)/7+1)= #temp > 0.
end loop.

You have discovered that MACROS are not too smart about arithmetic.
In fact Macro is just a string parser.  If it had gone to college it would have failed mathematics ;-).  If you want to do something like this and are absolutely committed to a macro solution I would urge you to study the Canonical Correlation Macro which ships with the Advanced statistics module.  It simulates multiplication (m*n) by concatenating a string to a given length (n) and then concatenating that string (m) times.  By checking the length of the mn string you have n*m as a macro string walla (sp) you have macro doing math (or something like it).

BTW.  When I used to do Technical Support I used to be the MACRO specialist.  The very first brain puller I received was somebody trying to get it to do math.  That one kept me busy for awhile until I realized Macro is numerically unaware ;-)  But since you have SPSS 7.5 the best way to do this is a script.

See the SPSSInfo object and its properties (in particular the VariableAt property).

*There is an example in the help file (copied below)*.

Dim objSpssInfo as ISpssInfo
Dim strVarName as String, strLabel as String
Set objSpssInfo = objSpssApp.SpssInfo
' Gets the variable names and reads the label for GENDER:

Dim Count as Integer, I as Integer
Count = objSpssInfo.NumVariables
For I = 0 To Count - 1
strVarName = objSpssInfo.VariableAt(I)
        If strVarName = "gender" Then
        strLabel = objSpssInfo.VariableLabelAt(I)
        Exit For
        End If
Next