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Dataplot Vol 2 Vol 1

Q QUANTILE RANGE

Name:
    Q QUANTILE RANGE (LET)
Type:
    Let Subcommand
Purpose:
    Compute the q quantile range for a variable.
Description:
    The q quantile range is defined as:

      QQ = X1-q - Xq

    where q defines a quantile between 0 and 0.5 and Xq denotes the q-th quantile of the data.

    For example, if q = 0.20, then the q quantile range is the difference between the 80th and 20th quantiles of the data. The interquartile range is a special case of the q quantile range with q = 0.25.

    The q quantile range is used as a robust measure of scale.

Syntax:
    LET <par> = Q QUANTILE RANGE <y>
                            <SUBSET/EXCEPT/FOR qualification>
    where <y> is the response variable;
                <par> is a parameter where the computed q quantile range is stored;
    and where the <SUBSET/EXCEPT/FOR qualification> is optional.
Examples:
    LET A = Q QUANTILE RANGE Y1
    LET A = Q QUANTILE RANGE Y1 SUBSET TAG > 2
Note:
    The desired quantile is specified with the following command

      LET QUANT = <value>

    If <value> is between 1 and 100, it is interpreted as as percentile (i.e., the quantile will be determined by dividing by 100). If <value> is between 0.5 and 1, then 1 - <value> will be used. If <value> is less than or equal to 0 or greater than or equal to 100, an error message will be printed.

Note:
    Dataplot statistics can be used in a number of commands. For details, enter

Default:
    None
Synonyms:
    QQUANTILE RANGE is a synonym for Q QUANTILE RANGE.
Related Commands: Reference:
    Rand Wilcox (1997), "Introduction to Robust Estimations and Hypothesis Testing," Academic Press, pp. 24-25.
Applications:
    Robust Data Analysis
Implementation Date:
    2012/9
Program 1:
    LET Y1 = LOGISTIC RANDOM NUMBERS FOR I = 1 1 1000
    LET Y2 = DOUBLE EXPONENTIAL RANDOM NUMBERS FOR I = 1 1 1000
    LET Y3 = NORMAL RANDOM NUMBERS FOR I = 1 1 1000
    LET QUANT = 0.10
    LET A1 = Q QUANTILE RANGE Y1
    LET A2 = Q QUANTILE RANGE Y2
    LET A3 = Q QUANTILE RANGE Y3
    PRINT A1 A2 A3
        
    The following output is generated.
     PARAMETERS AND CONSTANTS--
    
        A1      --         4.1971
        A2      --         3.1889
        A3      --         2.4609
        
Program 2:
     
    SKIP 25
    READ GEAR.DAT DIAMETER BATCH
    TITLE AUTOMATIC
    TITLE CASE ASIS
    XLIMITS 1 10
    MAJOR XTIC MARK NUMBER 10
    MINOR XTIC MARK NUMBER 0
    XTIC OFFSET 1 1
    X1LABEL BATCH
    X2LABEL Q = 0.20
    Y1LABEL Q QUANTILE RANGE OF DIAMETER
    CHARACTER CIRCLE
    CHARACTER FILL ON
    CHARACTER HW 2 1.5
    LINE BLANK
    LET QUANT = 0.20
    Q QUANTILE RANGE PLOT DIAMETER BATCH
        

    plot generated by sample program

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Date created: 09/07/2012
Last updated: 10/07/2016

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