Date:         Thu, 29 Sep 2005 11:26:21 -0400
Reply-To:     Richard Ristow <wrristow@mindspring.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Richard Ristow <wrristow@mindspring.com>
Subject:      Re: Finding information on +
Comments: To: Martin Sherman <MSherman@loyola.edu>
In-Reply-To:  <s33bb94e.096@GWMAIL01.LOYOLA.EDU>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 09:52 AM 9/29/2005, Martin Sherman wrote:

>My help command on SPSS 13.0 is not functioning

So, you're helpless? <Sorry. I'm flaky this morning>

>I am trying to get a handle on the use of the  + sign in a do if
>loop.  Is it
>simply allowing one to use a do if within a do if?
[For example,]
>do if nmiss(pcl_b, pcl_c, pcl_d) eq 0.
>+ Do if (pcl_b ge 1 and pcl_c ge 3 and pcl_d ge 2).
>+ compute pcl_dsm3=1.
>+ else if (pcl_b lt 1 or pcl_c lt 3 or pcl_d lt 2).
>+ compute pcl_dsm3=0.
>+ end if.
>Else.
>Compute pcl_dsm3 eq 9.
>End if.

The '+' sign is for the appearance of the code, only, though the
appearance is important.

In interactive syntax rules, a statement has to start at the left
margin. To allow "indenting" for readability, SPSS counts a '+', '-' or
'.' in the left margin as the beginning of a statement; the keyword can
then follow anywhere on the line.

(Raynald Levesque pointed out a while ago that '-' and '.' can be safer
than '+', which sometimes can be confused with the '+' that signifies a
string is continued on the next line. You aren't using string literals,
so that's OK.)

You can always use a DO IF construct within another one, though you
have to be sure your END IFs are in the right place. The code you
wrote,

do if nmiss(pcl_b, pcl_c, pcl_d) eq 0.
+ Do if (pcl_b ge 1 and pcl_c ge 3 and pcl_d ge 2).
+ compute pcl_dsm3=1.
+ else if (pcl_b lt 1 or pcl_c lt 3 or pcl_d lt 2).
+ compute pcl_dsm3=0.
+ end if.
Else.
Compute pcl_dsm3 eq 9.
End if.

is equivalent to

do if nmiss(pcl_b, pcl_c, pcl_d) eq 0.
Do if (pcl_b ge 1 and pcl_c ge 3 and pcl_d ge 2).
compute pcl_dsm3=1.
else if (pcl_b lt 1 or pcl_c lt 3 or pcl_d lt 2).
compute pcl_dsm3=0.
end if.
Else.
Compute pcl_dsm3 eq 9.
End if.

but that's nowhere near as readable. On the other hand, you can (and I
would) go yet farther with the indenting:

do if nmiss(pcl_b, pcl_c, pcl_d) eq 0.
+ Do if (pcl_b ge 1 and pcl_c ge 3 and pcl_d ge 2).
+   compute pcl_dsm3=1.
+ else if (pcl_b lt 1 or pcl_c lt 3 or pcl_d lt 2).
+   compute pcl_dsm3=0.
+ end if.
Else.
+ Compute pcl_dsm3 eq 9.
End if.

That is, two spaces of "indenting" for each construct the statement is
within.