parcoord.hlp.htm

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help for parcoord                                             (STB-29: gr18)
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graph multivariate data in parallel coordinates
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   parcoord varlist [if exp] [in range] 
             [, by(byvar) center colorby(idvar) echo tour graph_options] 

Description
-----------

parcoord draws a parallel coordinates plot for the variables in varlist.  A
parallel coordinates plot provides an alternative to the scatterplot matrix for
visually examining many variables simultaneously. Variables in varlist are rep-
resented as parallel vertical axes; each observation is plotted as a collection
of line segments joined end-to-end.  Subsets of observations can be selected
with if and in clauses; an observation will be ignored if it has missing values 
for any of the byvar, idvar, or varlist variables.

Options
-------

by(byvar) uses the by option of the graph command to draw a separate plot for
    each value of byvar.  The graph option total may be used with this option.

center scales each axis so that the median of the corresponding variable falls
    at the midpoint and all data fall within the length of the axis.  The de-
    fault is to scale each axis to extend from the minimum to the maximum value
    of the variable represented.

colorby(idvar) assigns different pens to observations with different values of
    idvar.  On color monitors, this displays subsets of observations (defined
    by idvar) in different colors.

echo prints the names of the axes (variables), in left-right order, to the Results 
screen before drawing the plot.  (Useful if the number of variables
    is large and the variable names are hard to read in the plot.)

tour generates a sequence of plots by repeatedly permuting the left-right order
    of the variables in the plot.  By default, axes are drawn in the same order
    that the variables appear in the varlist.  tour permutes the axes such that
    each possible pair of the p variables in varlist is represented on adjacent
    axes within the first (p+1)/2 plots of the tour. The tour pauses after each
    plot and displays --more--.  The tour continues endlessly, until the user
    presses the Break key, although the tour is largely redundant after the
    first (p+1)/2 plots.

graph_options are any of the options allowed with graph, twoway, except for:
    by, b2title, connect, noaxis, pen, symbol, tlabel, xlabel, xline, ylabel,
    yline.

Examples
--------

 . parcoord ftime*, center
   (plot all variables whose names begin with ftime. Variables assigned to axes
   in the same order that they appear in the data set; axes scaled so that the
   median of each ftime variable is at the axis midpoint.)

 . parcoord xa1 xa2 yb1 yb2 yb3 yb4 if time > 50, col(trt)
   (one 6-dimensional parallel coordinates plot for all cases where time > 50;
   observations at different values of trt drawn in different colors.)

 . parcoord bwt1-bwt12 if !censor, by(site) tour echo
   (sequence of graphs for cases where censor == 0; each graph contains a par-
   allel coordinates plot for each value of site.  Successive graphs alter the
   left-right order of the variables bwt1-bwt12 within each plot; that ordering
   is printed to the Results screen before each graph is drawn.)

Author
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        John R. Gleason
        Syracuse University
        73241.717atcompuserve.com


Also see
-------- 

    STB:  STB-29 gr18
 Manual:  [3] by, [3] matrix, [3] pens
On-line:  help for graph@, scatterplot