next up previous contents index
Next: High resolution plots Up: Plotting data Previous: Labelling plots

Low resolution plots

 
tex2html_wrap_inline33790 tex2html_wrap_inline33790 Syntax

BD>loplot : N1, B1 [=L1] [, B2 [=L2]] ... tex2html_wrap_inline33712

where N1 is the name of a data-carrier; tex2html_wrap_inline39952 are the names of bases of data-carriers, or the names of single data-carriers; and tex2html_wrap_inline39954 are the names of data-carriers.

tex2html_wrap_inline33806 tex2html_wrap_inline33806

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 tex2html_wrap_inline39930 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 tex2html_wrap_inline39930 , 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.)

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 tex2html_wrap_inline39934 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 tex2html_wrap_inline39936 labelled by za, superimposes a plot of the n pairs tex2html_wrap_inline39938 also labelled by za, superimposes a plot of the n pairs tex2html_wrap_inline39940 labelled by zb, and finally superimposes a plot of the n pairs tex2html_wrap_inline39942 unlabelled. The title of the plot as as defined in the preceding TITLE:  command.

  figure17677
Figure 17.1:  Example code for a low resolution plot

 


next up previous contents index
Next: High resolution plots Up: Plotting data Previous: Labelling plots

David Wooff
Wed Oct 21 15:14:31 BST 1998