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Bringing data to a common unit

Problem

You want to bring to a common unit of measurement numeric data which was collected on different units.

Solution

There are two possibilities:

  • if the unit multipliers are integers, assign the multiplier to the unit and perform a multiplication;
  • if the unit multipliers are not integers, user the ternary operator in a calculation.

Discussion

First, a note of clarification on the actual problem. This recipe discusses the situation where numeric data was collected (e.g., one's weight or one's salary) which requires a numeric value as well as a unit of measurement (e.g., inches vs. centimiters, dollars per hour, per week, per month), typically collected using a unit-type question. The questionnaire designer wants to calculate a unique value which will bring all responses to a common unit (e.g., centimiters or dollars per year).

If the unit multipliers are integers, it is possible to assign the multiplier as the category code for the unit and to simply multiply this code with the numeric value supplied. For example:

    SALARY
    % question
       What is your salary?
    % note
    % categories
       *998*N*amount
       *40*per hour
       *5*per day
       *1*per week
       *999*Don't know/no answer
    % skips
    % condition
    % open
       998 = N7.2 1 5000
    ! ==============================================================
    PERWEEK CALCUL
    % question
       APERWEEK = $SALARY * $ASALARY
    % note
    % categories
     
    % skips
    % condition
       SALARY.EQ.1,5,40
    % open
       1 = N7.2 1 5000 FORMAT=DOLLAR2
    ! ==============================================================

If the unit multipliers are not integers (a limitation of answer category codes), use a calculation and the ternary operator (the "implicit if" operator). For example:

    HEIGHT
    % question
       How tall are you?
    % note
    % categories
       *998*N*amount
       *1*centimeters
       *2*inches
       *999*Don't know/no answer
    % skips
    % condition
    % open
       998 = N7.2 48 200
    ! ==============================================================
    INCENTIMETERS CALCUL
    % question
       AINCENTIMETERS = $AHEIGHT * ( ( $HEIGHT == 1 ) ? 1 : 2.54 )
    % note
    % categories
     
    % skips
    % condition
       HEIGHT.EQ.1,2
    % open
       1 = N7.2 48 200 FORMAT=NUM0
    ! ==============================================================

   

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