
BOX COX NORMALITY PLOTName:
For each of selected members of the BoxCox family, the transformation is carried out, a normal probability plot is computed, and the linearity of the normal probability plot is summarized via the correlation coefficient. The resulting normality plot thus consists of:
The value of the lambda parameter (on the horizontal axis) which corresponds to the maximum of the normal probability plot correlation coefficient curve (on the vertical axis) is of interest since it indicates the besttransformation member of the family. The normality technique is applicable for general transformation families. Currently, DATAPLOT only implements it for the BoxCox family (the most important and common of the various transformation families).
<SUBSET/EXCEPT/FOR qualification> where <y> is a response variable; and where the <SUBSET/EXCEPT/FOR qualification> is optional. This syntax generates a single BoxCox normality plot. Note that <y> can also be a matrix argument. If <y> is a matrix, a single BoxCox normality plot is generated for all the values in the matrix.
<SUBSET/EXCEPT/FOR qualification> where <y1> ... <yk> is a list of response variables; and where the <SUBSET/EXCEPT/FOR qualification> is optional. Note that response variables can also be matrices. If a matrix name is encountered, a BoxCox normality plot will be drawn for all the values in the matrix.
<SUBSET/EXCEPT/FOR qualification> where <y> is a response variable; <x1> is a groupid variable; and where the <SUBSET/EXCEPT/FOR qualification> is optional. A BoxCox normality plot will be generated for each distinct value of the groupid variable. These plots will be overlaid on the same plot.
<SUBSET/EXCEPT/FOR qualification> where <y> is a response variable; <x1> is a groupid variable; <x2> is a groupid variable; and where the <SUBSET/EXCEPT/FOR qualification> is optional. The two groupid variables are crosstabulated and a BoxCox normality plot will be generated for each distinct combination of values for the groupid variables. These plots will be overlaid on the same plot.
BOXCOX NORMALITY PLOT Y2 MULTIPLE BOXCOX NORMALITY PLOT Y1 TO Y5 REPLICATED BOXCOX NORMALITY PLOT Y X1
LET A = BOX COX NORMALITY LAMBDA Y These return the maximum PPCC value on the BoxCox normality plot and the corresponding value of lambda, respectively. These statistics can be used in a large number of plots and commands. For details, enter
2010/5: Support for MULTIPLE and REPLICATION options LET Y = EXPONENTIAL RANDOM NUMBERS FOR I = 1 1 100 Y1LABEL CORRELATION COEFFICIENT X1LABEL LAMBDA BOXCOX NORMALITY PLOT YProgram 2: title case asis title offset 2 title automatic label case asis multiplot corner coordinates 0 0 100 95 multiplot scale factor 2 tic mark offset units screen y1tic mark offset 2 0 . let y1 = norm rand numb for i = 1 1 100 let y2 = logistic rand numb for i = 1 1 100 let y3 = double exponential rand numb for i = 1 1 100 let y4 = gumbel rand numb for i = 1 1 100 multiplot 2 2 box cox normality plot y1 box cox normality plot y2 box cox normality plot y3 box cox normality plot y4 end of multiplot move 50 97 just center text Normal/Logistic/Double Exponential/Gumbel Random Numbers . line color blue red green cyan multiple box cox normality plot y1 to y4 . reset data skip 25 read rehm.dat y1 y2 x1 x2 . line color blue red green replicated box cox normality plot y1 x2
 
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Date created: 11/30/2010 