By joining a table onto itself, you can look at expressions of values
from the same column but different records. For example, suppose you
want to plot the derivative of column
NE where you have NE as a function of
RADIUS and TIME, and TIME is evenly spaced with an
increment of 0.01 seconds. You would join this table with itself, such
that the rows are offset. To do this, first go back to the top menu
(`\0`

) and select *two copies* of the table: `PT GP8840
GP8840;`. Then select the JOIN option and define the join as
`(A.TIME-0.01=B.TIME)AND(A.RADIUS=B.RADIUS)`. Now for the *y*
axis, you can specify `(A.NE-B.NE)/(A.TIME-B.TIME)` as in
Figure 7.

\* Options are: 1) Y < (A.NE-B.NE)/(A.TIME-B.TIME) > 2) X < TIME > 3) Constraints < RADIUS=70 (TIME>2.8)AND(TIME<3.4) > 4) Symbols < > 5) Graph ranges <Y:0.00E+00,0.00E+00,LIN><X:0.00E+00,0.00E+00,LIN> 6) G+ Graph Plus <Auto-scale_Y:min=T,max=T><Auto-scale_X:min=T,max=T> 7) Key for dynamic cursor option <A.NE> 8) Join <(A.TIME-0.01=B.TIME)AND(A.RADIUS=B.RADIUS)> ...A join of

**Figure 7:** Plot a derivative by joining a table with itself

Fri Jul 11 17:05:56 EDT 1997