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Dataplot Vol 1 Vol 2

SHIFT PLOT

Name:
    SHIFT PLOT
Type:
    Graphics Command
Purpose:
    Generates a shift plot.
Description:
    The shift plot is a plot of

      yq - xq versus xq

    with yq and xq denoting the qth quantiles of y and x, respectively. Although this plot can be generated for any pair of variables, the primary usage of this plot is for the case where x is a control group and y is an experimental method. Alternatively, x could represent an "old" method while y represents a "new" method. The plot measures how much the control group must be shifted so that it is comparable to the expermimental method (relative to the quantiles).

    The quantiles of a distribution are the distribution's "percent points" (e.g., the 0.5 quantile = the 50% point = the median).

    The plot consists of the following:

      Vertical axis = difference in the estimated quantiles between data set 1 and data set 2;

      Horizontal axis = estimated quantiles from data set 2.

    The shift plot is a variation of the quantile-quantile plot and the Tukey mean-difference plot.

Syntax 1:
    SHIFT PLOT <y> <x>       <SUBSET/EXCEPT/FOR qualification>
    where <y> is the response variable for the experimental group;
                <x> is the response variable for the control group;
    and where the <SUBSET/EXCEPT/FOR qualification> is optional.

    With this syntax, the quantiles correspond to the data points of the <x> variable.

Syntax 2:
    SHIFT PLOT <y> <x> <q>       <SUBSET/EXCEPT/FOR qualification>
    where <y> is the response variable for the experimental group;
                <x> is the response variable for the control group;
                <q> is a variable (with values between 0 and 1) that specifies the desired quantiles to plot;
    and where the <SUBSET/EXCEPT/FOR qualification> is optional.

    With this syntax, you explicitly give the desired quantiles.

Examples:
    SHIFT PLOT Y X
    SHIFT PLOT Y X SUBSET X > 1
    SHIFT PLOT Y X XQ
    SHIFT PLOT Y X XQ SUBSET X > 1
Default:
    None
Synonyms:
    None
Related Commands: Reference:
    Rand R. Wilcox (1997), "Introduction to Robust Estimation and Hypothesis Testing", Academic Press.
Applications:
    Exploratory Data Analysis
Implementation Date:
    2003/2
Program:
     
    SKIP 25
    READ AUTO83B.DAT Y1 Y2
    .
    DELETE Y2 SUBSET Y2 < 0
    LABEL CASE ASIS
    Y1LABEL Difference between Y1 and Y2 Quantiles
    X1LABEL Quantiles for Y2
    CHARACTER X
    LINE BLANK
    SHIFT PLOT Y1 Y2
        

    plot generated by sample program

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Date created: 2/28/2003
Last updated: 10/19/2015

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