Overlays are added by the S2/S3/... and D2/D3/... commands. Overlays can be used to display more data elements on the page for a single shot, or to compare one or two data elements over multiple shots. The default number of curves on startup or after the Initialize command is 2, the number of frames is 32. Once data has been read in to CUPLOT, you refer to it using the notation FnCm, where Fn is frame n and Cm is curve m. As a shorthand, Fn is the same as FnC1. The full matrix of data elements is:
D1 F1C1 F2C1 F3C1 . . .
D2 F1C2 F2C2 F3C2 . . .
. . .
. . .
Note that DE clears all data elements, not just the D1 elements. D2/D3/..., like D1, remember any existing names. The SH command clears all the shot numbers; there is no S1.
This example plots 2 devices for 6 consecutive shot numbers, as seen in Figure 2. Note that when specifying the shot number for each overlay curve Sn, ``.'' refers to the SH shot, not the shot for the previous overlay.
NC 6 !allow more overlays
DE D-PTOT NE-SS-CW ;
XT 2.5 4.5
S2 .-1 S3 .-2 S4 .-4 S5 .-5 S6 .-6
Figure 2: Beam power and neutron strength for six shots
If you use the ``.+n'' and ``.-n'' notation in the S2/S3/... commands, the overlay shot number(s) are referenced to the SH shot:
SH LAST !most recent shot
S2 .-1 !shot before that
The XC/YC (scaling) commands request the offset and multiplier for each different data element. The YD (description) and YL (units) commands request a value for each frame.