**Figure 11:** Scattered surface plot

**Figure 12:** Smoothed surface plot

SURFACE lets you plot data as a function of two variables.
You can get an isometric graph of raw data or of smoothed data. After
you select SURFACE from the main menu, you will be prompted
for the axis variables. You can set constraints and the axis ranges.
If you select the scatter plot which is the default, you will get a
symbol plotted on an isometric graph for each point that satisfies the
constraints. See Figure 11. If you select to
interpolate, you can choose to use the *x* and *y* values of your
database for the grid. An interpolation of *z* is done at these
coordinates as shown in Figure 12. Alternatively, you
can specify an evenly spaced grid for either *x* or *y* and *z* will
be interpolated on that grid. The interpolation is done by the
IMSL routine SURF . SURF
``computes a smooth bivariate interpolant to scattered data which is
locally a quintic polynomial in two variables.''[7] To produce
a graph with SURFACE:

<2;> X, Y, Z? < >: radius time ne <5=S;> Set X, Y, Z, XA, YA, ZA, C, T, Sc, In? <C>: \* Options are: 1) X <RADIUS> 2) Y <TIME> 3) Z <NE> 4) XAxis range < 0.000E+00, 0.000E+00, LIN > 5) YAxis range < 0.000E+00, 0.000E+00, LIN > 6) ZAxis range < 0.000E+00, 0.000E+00, LIN > 7) Constraints < > 8) Title <> 9) Scatter plot of raw data <ON> or 10) Interpolate the data onto a regular grid <OFF> <5=S;> Set X, Y, Z, XA, YA, ZA, C, T, Sc, In? <C>: ;

Fri Jul 11 17:05:56 EDT 1997