Four types of variables can appear in the listing from
PROC TIMEPLOT: plot variables, ID variables, class variables, and
symbol variables (as part of some column headings). Plot variables
and symbol variables can also appear in the plot.
Observations with missing
values of a class variable form a class of observations.
In the listing, missing
values appear as a period (.), a blank, or a special missing value
(the letters A through Z and the underscore (_) character).
In the plot, PROC TIMEPLOT
handles different variables in different ways:
-
An observation or class of observations
with a missing value of the plot variable does not appear in the plot.
-
If you use a symbol variable
(see the discussion
of plot requests), then PROC TIMEPLOT uses a period
(.) as the symbol variable on the plot for all observations that have
a missing value for the symbol variable.