
PERCENT POINT PLOTName:
Thus, for example, if the value of 50 is chosen on the horizontal axis, then the corresponding value on the vertical axis is the estimated 50% point (that is, the median) from the data. The percent point plot can be generated for either raw data or for binned data. For raw data, the percentile plot is constructed by plotting the sorted data on the vertical axis. The corresponding horizontal axis value for the ith point is 100*Y_{i}/N with Y_{i} and N denoting the ith observation of the sorted data and the sample size, respectively. The multiplication by 100 is to covert the horizontal axis to a percentage value. For binned data, the vertical axis value is the midpoint of the bin. The corresponding horizontal axis values are the cumulative sums of the frequencies of the bins divided by the sum of the frequencies for all bins. This value is multiplied by 100 to convert the horizontal axis to a percentage value. By default, raw data is first binned into frequency data. To suppress this binning (i.e., generate the raw data version of the plot), enter the command
To restore the default of binning raw data, enter
Typically no binning is preferred for small to moderate size data sets. Binning can be helpful for large data sets in that it reduces the number of points that are plotted.
where <x> is the variable of raw data; and where the <SUBSET/EXCEPT/FOR qualification> is optional. This syntax is used for the case where you have raw data.
where <y> is the variable of precomputed frequencies; <x> is the variable of distinct values; and where the <SUBSET/EXCEPT/FOR qualification> is optional. This syntax is used for the case where you have precomputed frequencies at each data level. This syntax is used when you have equal width bins.
<SUBSET/EXCEPT/FOR qualification> where <y> is the variable of precomputed frequencies; <xlow> is the variable containing the lower limits of the bins; <xhigh> is the variable containing the upper limits of the bins; and where the <SUBSET/EXCEPT/FOR qualification> is optional. This syntax is used for the case where you have precomputed frequencies at each data level. This syntax is used when you have unequal width bins.
<SUBSET/EXCEPT/FOR qualification> where <y1> ... <yk> is a list of 1 to 30 response variables; and where the <SUBSET/EXCEPT/FOR qualification> is optional. This syntax will generate percent point plots of each of the listed response variables on the same plot. You can specify different plot attributes for each response variable. This syntax is only supported for raw data (i.e., no binned data).
<SUBSET/EXCEPT/FOR qualification> where <y> is the response variable; <x1> ... <xk> is a list of 1 to 6 groupid variables; and where the <SUBSET/EXCEPT/FOR qualification> is optional. From one to six groupid variables can be specified (most commonly there is a single groupid variable). Note that with this syntax, the plot points corresponding to each group are drawn with different attributes (i.e., the first group uses the first setting for the CHARACTER and LINE and related attribute setting commands, the second group uses the second setting, and so on). For example, this syntax can be used to label the plot points with the groupid. If there is more than one groupid variable, the attribute settings work from right to left. That is, if X1 has 2 levels and X2 has 2 levels, then
<SUBSET/EXCEPT/FOR qualification> where <y> is the response variable; <x> is a groupid variable; and where the <SUBSET/EXCEPT/FOR qualification> is optional. Although this syntax is similar to the REPLICATION case, it is generally used in a different way. The REPLICATION case is used when we have distinct groups of data and we want to generate separate percent point plots for each group. Highlighting is used when we have a single group of data, but we want to draw some of the points with different attributes. For example, we may want to emphasize the extreme points in the plot.
PERCENT POINT Y X PERCENT POINT Y XLOW XHIGH HIGHTLIGHTED PERCENT POINT Y TAG MULTIPLE PERCENT POINT Y1 Y2 Y3 PERCENT POINT Y X SUBSET X > 2
The SET HISTOGRAM CLASS WIDTH can be used to define several other algorithms for binning the data (HELP HISTOGRAM CLASS WIDTH for details). The SET HISTOGRAM OUTLIERS command also applies to the PERCENT POINT PLOT if raw data is being binned.
1998/09: Support for SET PERCENT POINT PLOT command. 2011/02: Support for REPLICATION and MULTIPLE options. 2011/02: Support for HIGHLIGHT option. SKIP 25 READ SUNSPOT2.DAT Y . LET ALOW = MINIMUM Y LET AHIGH = MAXIMUM Y CLASS LOWER ALOW CLASS UPPER AHIGH CLASS WIDTH 1.0 CHARACTER CIRCLE CHARACTER FILL ON CHARACTER SIZE 1.2 X1LABEL PERCENT POINT Y1LABEL DATA VALUE TITLE AUTOMATIC . PERCENT POINT PLOT YProgram 2: let y1 = norm rand numb for i = 1 1 100 . title case asis title offset 2 title automatic label case asis tic mark offset units screen tic mark offset 3 3 . char circle char fill on char hw 0.5 0.375 line blank . multiplot corner coordinates 5 5 95 95 multiplot scale factor 2 multiplot 2 2 . set percent point plot unbinned set histogram outliers on set histogram empty bins off title Unbinned Data percent point plot y1 . set percent point plot binned title Data Binned by Command percent point plot y1 . title User Created Bins: EquiSpaced Bins let z2 x2 = binned y1 percent point plot z2 x2 . let minsize = 5 let z3 xlow xhigh = combine frequency table z2 x2 title User Created Bins: UnequalSpaced Bins percent point plot z3 xlow xhigh . end of multiplot justification center move 50 97 text Percent Point Plots for 100 Normal Random Numbers move 50 5 text Percentile direction vertical move 3 50 text Response ValueProgram 3: dimension 500 rows skip 25 read iris.dat y1 y2 y3 y4 let m = create matrix y1 y2 y3 y4 . title case asis title offset 2 label case asis . char circle all char color black char fill on all char hw 0.5 0.375 all line blank all . y1label Response Value x1label Percentile title IRIS Data (all species combined) . set percent point plot unbinned set histogram outliers on set histogram empty bins off percent point plot m . char color red blue cyan green title IRIS Data (species plotted separately) multiple percent point plot y1 to y4 Program 4: skip 25 read gear.dat y x . title case asis title offset 2 label case asis tic mark offset units screen tic mark offset 5 5 . char circle all char color black red blue green cyan grey brown magenta dgreen orange char fill on all char hw 0.5 0.375 all line blank all . title Percent Point Plots for GEAR.DAT y1label Response Value x1label Percentile . set percent point plot unbinned set histogram outliers on set histogram empty bins off replicated percent point plot y x  
Date created: 06/04/2016 Last updated: 12/04/2023 Please email comments on this WWW page to alan.heckert@nist.gov. 