/*****************************************************************************************************************

SAS file name: Replace_Missing_With_Previous.sas
File location: 
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Purpose: To demonstrate how to replace missing values with the previous/most recent non missing value
Author: Peter Clemmensen
Creation Date: 01/12/2017

This program supports the post "Replace Missing Values with Previous" on SASnrd.com

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/* Example Data */
data MyData;
input ID$ Value;
datalines;
1 2
1 .
1 .
1 4
2 .
2 9
2 .
2 .
3 3
3 .
3 0
;

/* Make sure that data is sorted correctly */
proc sort data=MyData;
   by ID;
run;

/* Replace missing values with previous by group */
data Want;
   update MyData(obs=0) MyData;
   by ID;
   output;
run;