BD>loplot : N1, B1 [=L1] [, B2 [=L2]] ...
where N1 is the name of a data-carrier;
The LOPLOT: command is used to produce low-resolution plots. The
command has at least two arguments. N1 is the name of the data carrier
to appear on the x-axis. The remaining arguments
Each data carrier to appear on the y-axis can be associated with a
labelling vector L. Further, if a base name rather than the name of a
data-carrier is associated with a labelling vector, then this labelling
vector is associated with every data carrier in the base.
For low resolution plots, it is not possible to connect consecutively
plotted points with a straight line; nor is it possible to disable the
plotting of points. Consequently, the connect and
nopoints options are ignored here.
It is possible to change the resolution of the low resolution plots via
the plotlines and plotcols . These are, by default, 18
and 75 respectively, although they may be varied between 10 and 253; and
30 and 250 respectively. Each possible point location is a character
point on the screen.
Up to 26 superimposed plots are allowed, although there may be
insufficient space to report information about all of them on the plot,
and the plot itself may be hard to interpret. For unlabelled plots, and
where there are three or
fewer superimposed plots, special characters are plotted for the different
y-axis quantities. For four or more unlabelled plots, the letters of
the alphabet A..Z are plotted for the y-axis quantities.
If several points hit the same plotting address, the number of counts
is plotted (a nine represents nine or more counts).
It is possible to plot with a single quantity appearing on the y-axis
and up to 26 quantities appearing on the x-axis, instead. This will be
the effect of the PLOT: command if the plotxyy control
has been switched off. Otherwise the appearance of the plot is governed
by the same considerations.
The amount of data plotted will depend on the number of cases for which
observations exist on the single data-carrier to appear on the x-axis (or
instead the
y-axis if the plotxyy control has been switched off). If the
autoselect control is switched on, then all possible cases will
be included. Otherwise, if a data selection has been made using the
SELECT: command, only the cases
which have been selected and for which observations on the single
data carrier exist will be included. Finally, any points corresponding
to missing data are ignored.
As an example, consider the sequence of commands given in
Figure 17.1.
(See also the example given in
Figure 17.2 for a high resolution plot, and the example shown
in Figure 17.3 where we have a single y-axis quantity and
multiple x-axis quantities.)
Assume that
are the names
of bases of data-carriers, or the names of single data-carriers; and
are the names of data-carriers.
define a collection of quantities, each of which will appear on the
y-axis. The result will be several superimposed plots of N1 versus
each quantity in , all plotted to the same scale.
(Clearly the quantities to appear simultaneously on the y-axis should
be of similar magnitude, otherwise the superimposed plots will be
cramped in different regions of the overall plot.)
are all
data carriers of length n. The initial commands deal with organising
the amount of data to be plotted: only the cases for which the data
carrier x has values less than 0.5 will be considered.
The remaining commands construct a base
ua to contain two data carriers u1, u2, and then construct a plot
of the n pairs 
labelled by za, superimposes a plot of
the n pairs 
also labelled by za, superimposes a plot
of the n pairs 
labelled by zb, and finally
superimposes a plot of the n pairs 
unlabelled.
The title of the plot as as defined in the preceding TITLE:
command.
Figure 17.1: Example code for a low resolution plot
