CODEWITHSUNDEEP
if-statementsas
Gabriel Brodowski
Gabriel Brodowski

Reputation: 33

SAS Nested If Statements Producing Incorrect Result

ID no. 6 returns 'Underweight' when it should return 'Overweight'. The lines of code in question, lines 30-53, contain nested if statements and produce a single undesirable result. The purpose of these lines is to partition the sample into classifications of weight class: Underweight, Average or Overweight.

TITLE 'A SHORT SAS PROGRAM';
OPTIONS LS=72;
* Create data file with height and weight data;

DATA HTWT;
    INPUT ID GENDER $ HEIGHT WEIGHT;
    DATALINES;
1 M 68.5 155.0
2 F 61.2 99.00
3 F 63.0 115.0
4 M 70.0 205.0
5 M 68.6 170.0
6 F 65.1 125.0
7 M 72.4 220.0
;
    * Create a new categorical variable for height;

DATA HTWT;
    SET work.HTWT;

    IF HEIGHT < 68 THEN
        STATURE='Short';

    IF HEIGHT >=68 THEN
        STATURE='Tall';
RUN;

* Create a new categorical variable for weight;

DATA HTWT;
    SET work.HTWT;

    IF GENDER='M' THEN
        IF WEIGHT > 170 THEN
            WEIGHT_CLASS='Overweight';

        IF 170 >=WEIGHT >=150 THEN
            WEIGHT_CLASS='Average';

        IF WEIGHT < 140 THEN
            WEIGHT_CLASS='Underweight';

        ELSE IF GENDER='F' THEN
            IF WEIGHT > 120 THEN
                WEIGHT_CLASS='Overweight';

            IF 120 >=WEIGHT >=100 THEN
                WEIGHT_CLASS='Average';

            IF WEIGHT < 100 THEN
                WEIGHT_CLASS='Underweight';
        RUN;

        * Changing units of height from inches to centimeters;

        DATA HTWT;
            SET work.HTWT;
            HEIGHT=2.54 * HEIGHT;
        RUN;

        * Creates HEALTH_INDEX;

        DATA HTWT;
            SET work.HTWT;
            HEALTH_INDEX=WEIGHT/HEIGHT;
        RUN;

        * Print the data file HTWT;

        PROC PRINT DATA=HTWT;
            TITLE 'HEIGHT AND WEIGHT DATA';
        RUN;

        * Sorts the data by gender. Some procedures require sorted data;

        PROC SORT DATA=HTWT OUT=sorted;
            BY GENDER;
        RUN;

        * Print the sorted data file;

        PROC PRINT DATA=sorted;
            TITLE 'GENDER SORTED HTWT DATA';
        RUN;

Upvotes: 0

Views: 5466

Answers (4)

Nat Wooding
Nat Wooding

Reputation: 1

If statements are useful but sometimes it is safer to create a format and use put statements to do the assignments. This is particularly true if you would have to do a lot of IFs since in my case at least, the more typing I do, the greater is my chance of screwing up.

The code with the put statements is a lot easier to check and maintain.

Upvotes: 0

stat
stat

Reputation: 669

Please, don't accept my answer as the correct one, 'cause I'm late and previos answers are clear and useful. But I'm here to give you a simple advice, when you have to concatenate a lot of nested if statement, please use select when statement (coming from sql language) to give a stratum to all possible variable's value.

data want;
set have;
if gender='M' then do;
select (weight);
   when (>x) weight_class='';
   when (<y) weight_class='';
   otherwise weight_class=''
end;
end;
else if gender='F' then do;
select (weight);
   when (>x) weight_class='';
   when (<y) weight_class='';
   otherwise weight_class=''
end;
end;
run;

Upvotes: 1

yukclam9
yukclam9

Reputation: 336

Modify your nested if statement into:

 IF  GENDER='M' THEN do;
     IF WEIGHT > 170 THEN
        WEIGHT_CLASS='Overweight';

    else if 150 <= Weight <= 170 THEN
        WEIGHT_CLASS='Average';

    else
        WEIGHT_CLASS='Underweight';
    end;

 else do;
    IF WEIGHT > 120 THEN
        WEIGHT_CLASS='Overweight';

    else iF 100 <= Weight =< 120 THEN
        WEIGHT_CLASS='Average';

    else
        WEIGHT_CLASS='Underweight';
 end;

See if it works?

Upvotes: 1

Tom
Tom

Reputation: 51566

Consecutive IF statements are processed in order. So since the last one is testing if WEIGHT is < 100 then of course number 6 is being listed as underweight. If you want to control execution order add some ELSE and/or DO/END blocks. Your basic structure probably should look like this.

if A then do;
  if B then xxx ;
  else if C then xxx ;
  else if D then xxxx ;
end;

Upvotes: 0

Related Questions