Transcript Health Related Quality of Life (HRQoL) in Metastatic

Jerry Tsai
[email protected]
This presentation and code available at:
clintuition.com/pubs/
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Efficiently Handle Lists of Items using the
SAS® Macro Language
--Save Time and Reduce Errors
Jerry Tsai
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Problem Statement
Working with a data set that contains many
variables often requires repeating the same
editing task over and over on those variables.
Problems with having to make repetitive edits:
 Increased chance of inconsistency, leading to
errors in syntax or in logic
 Increase in time required for task completion
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Data Set Examples
#1: Laboratory values
Variables: hemoglobin, hematocrit, MCH, MCV, RBC,
platelets, etc.
#2: Survey data
Variables: Question 1, Question 2, Question 3, etc.
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Desired Solution
Write code addressing these multiple items
with as little unnecessary repetition as
possible– and do it correctly the first time.
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Process Flow
 Write code that addresses one item on the
list and validate that it works as desired.
 Extend the validated code to all items on
the list.
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Method
 Edit the validated code for use with a
macro:
 Replace the list item with a wildcard character.
 With each iteration, this wildcard will be replaced
with a item on the list.
 The macro will iterate through the list
using a loop.
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MACRO %ITERLIST
Two parameters:

LIST
 CODE
%iterlist(list=, code=)
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Setup
Macro variable containing a space-delimited
list, e.g.:
%let mylist = alfa bravo charlie...yankee
zulu;
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Example #1: Renaming a List of Vars
data new;
set
old
(
rename =
(alfa = alfa_n)
)
;
run;
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Example #1: Renaming a List of Vars
data new;
set
Replace item with wildcard character, ‘?’
old
(
? = ?_n
rename =
(alfa = alfa_n)
)
;
run;
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Example #1: Renaming a List of Vars
data new;
set
old
(
rename =
(? = ?_n)
)
;
run;
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Example #1: Renaming a List of Vars
data new;
set
old
(
rename =
(
? = ?_n
)
)
;
run;
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Example #1: Renaming a List of Vars
data new;
set
old
(
rename =
(%iterlist(list = &mylist., code = %str(? = ?_n)))
)
;
run;
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Example #1: Renaming a List of Vars
data new;
set
old
(
rename =
(alfa = alfa_n
beta = beta_n ... zulu = zulu_n
)
)
;
run;
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Example #2: PROC MEANS statistics
proc means data = old;
var &mylist.;
output out
= oldstats (drop=_type_ _freq_)
n(alfa
)= alfa_nb
mean(alfa
)= alfa_mn
std(alfa
)= alfa_sd
;
run;
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Example #2: PROC MEANS statistics
proc means data = old;
var &mylist.;
output out
= oldstats (drop=_type_ _freq_)
%iterlist(list = &mylist., code = %str(
n(?)=?_nb))
%iterlist(list = &mylist., code = %str(mean(?)=?_mn))
%iterlist(list = &mylist., code = %str( std(?)=?_sd))
;
run;
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Example #3: Nested Macro Call
%macro printem(inputds =, variabl =);
proc print data=&inputds.;
var
&variabl.
;
run;
%mend
printem;
%printem(inputds = old, variabl = alfa);
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Example #3: Nested Macro Call
%iterlist
(
list = &mylist.,
code = %nrstr(
%printem(inputds = old, variabl = ?);
)
);
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Advantages of %ITERLIST()
 Robust approach separates programming
logic from the items being iterated over.
 Save programming time by avoiding
needless typing.
 By retaining the syntax of validated code,
reduce the likelihood of error.
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Noteworthy Aspects of %ITERLIST
 %DO-%END looping
 Macro quoting functions, e.g., %STR(),
%UNQUOTE()
 %QSYSFUNC()
 TRANWRD()
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Suggested Reading

Carpenter, Art. Resolving and Using &&var&i Macro
Variables - SUGI 22 Proceedings (1997)

Carpenter, Art. Storing and Using a List of Values in a
Macro Variable - SUGI 30 Proceedings (2005)

Morris, Robert. Text Utility Macros for Manipulating
Lists of Variable Names - SUGI 30 Proceedings (2005)

Clay, Ted. Tight Looping With Macro Arrays - SUGI
31 Proceedings (2006)
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Jerry Tsai
[email protected]
Questions? Comments?
This presentation and code available at:
clintuition.com/pubs/
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