Date:         Thu, 13 Feb 1997 10:24:02 -0800
Reply-To:     gxx18300@ggr.co.uk, BWRogers@MSN.COM
Sender:       "SAS(r) Discussion" <SAS-L@UGA.CC.UGA.EDU>
From:         Bruce Rogers <gxx18300@GGR.CO.UK>
Organization: Medical IR, Glaxo Wellcome
Subject:      Re: filling missing values with lagged values
Comments: To: Jennifer Soller <jennifer.soller@sf.frb.org>
Content-Type: text/plain; charset=us-ascii

Jennifer Soller wrote:
>
> Hello to all.
> Here's a little problem I was given by a friend
> who is pulling her hair out.
> Checked out past posts on dejanews to no avail.
> Hope someone can work their usual magic.
>
> I have the following dataset:
>
> OBS     X
> 1       1
> 2       .
> 3       .
> 4       2
> 5       2
> 6       2
> 7       .
> 8       3
> 9       3
> 10      .
> 11      .
> 12      .
> 13      .
> 14      4
> 15      .
>
> What I want is the following:
>
> OBS     X
> 1       1
> 2       1
> 3       1
> 4       2
> 5       2
> 6       2
> 7       2
> 8       3
> 9       3
> 10      3
> 11      3
> 12      3
> 13      3
> 14      4
> 15      4
>
> I want the missing values replaced by the previous
> non-missing value. I thought that:
<snip>
> I'm thinking about
> arrays and have read Ron Cody's array tutorials,
> but nothing is jumping out at me.
>
> Any advice?
> Much thanks.
 
Jennifer,
 
There is a _very_ simple way to achieve this, as follows:
 
DATA ONE (drop=tempvar);
  SET MYDATA;
  retain tempvar ;
  IF X = . THEN x = tempvar ;
  else tempvar = x ;
run;
 
I hope this is clear and self-explanatory - if you don't understand it
then I suggest you read up on the RETAIN statement.
 
Bruce