One method to extract QNFs from the simulation results is to use DV to produce
an appropriate 1D slice of the data, then use xvs' reduce function to
plot a given point as a function of time. 

In the following example, we assume that the real part of the Teukolsky
function is called "phre".

<ol>
<li> send phre to the DV (sdftodv phre)
<p>

<li> from the Functions window, clone phre with a filter to select
   the desired theta=constant slice of the data (we recommend slicing 
   along theta=pi/2). For example, if the dimension of phre is 65x33
   in (r,theta), then the following filter argument can
   be used (see <a href="/Doc/DV/sec_33.html#Other_functions"><b>HERE</b></a> for help on using filters)

<pre>
   ib = 1,65,17,17
</pre>

   Enter phre_slice (say) as the new name for the register, and click
   Go!
<p>

<li> On the DV main window, select phre_slice, and then 
"Write selected SDF(s) to disk" from the file menu, and save it to the 
local drive.
<p>

<li> From a shell, send the slice to xvs (sdftoxvs phre_slice.sdf).
<p>

<li> Use xvs' reduce -> y[j] function to plot the desired point as a function
of time.
</ol>