Re: implicit plot ??

pluton <plutonesque@xxxxxxxxx> wrote in message
<b98f1a0b-18fe-4bb4-832a-
a239b147f298@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>...
...........
I now want to plot the intersection of the surface with plane Z=0, and
I know
that it exists. Is there something like an implicit plot or something.
Or do I have to built this intersection by myself ?
----------------
Presumably in your second post when you say Z = 0 you mean that you want
to plot the points where DR equals zero.

The surface which 'surf' produces obtains its effect by drawing little line
segments connecting neighboring points in the k and omega mesh whose
endpoints are at the corresponding DR height values. I would suggest
locating those line segments among these which have opposite signs for DR
at the two endpoints, and doing a linear interpolation between them. In other
words, find all DR(q,p) and DR(q+1,p) pairs or DR(q,p) and DR(q,p+1) pairs
which are of opposite sign. This linear interpolation is a simple operation.
That would give you a large set of points which could be plotted. I am not
knowledgeable enough to know how to superimpose a plot of these points
together with the surface plot on the same graphic display, but I suspect
there is a way.

By the above interpolation I mean this. Suppose, say, DR(q,p) and DR(q
+1,p) have opposite signs. Call D! = DR(q,p) and D2 = DR(q+1,p). Then

(1-t)*D1+t*D2

represents the line segment between the two points with t as a parameter,
and it crosses zero at t = -D1/(D2-D1), which would correspond to the
argument q+t. Linear interpolation with k and Omega would place them at

k0 = (1-t)*k(p,q) + t*k(p,q+1) and
Omega0 = (1-t)*Omega(p,q) + t*Omega(p,q+1)

values. This gives you a point (k0,Omega0,0) to be plotted which would lie
on one of the surface line segments.

Roger Stafford

.

Relevant Pages

  • Re: Looking for an automated method for plotting the amplitude envelope of an audio signal
    ... tweaking the settings it doesn't seem to plot the signal's amplitude ... segments that connect them will actually cross the curve. ... also have an infinite first derivative, ...
    (comp.dsp)
  • Re: Sierpinski polygons
    ... class of IFS attractors composed of rings of identical, touching, ... can plot the rotations and contractions which produce such attractors; ... the plot contains line segments where you can continuously adjust one to ... some isolated point or line segments. ...
    (sci.fractals)
  • Re: plot short segments from a very large data file
    ... > short segments of the data. ... I only needed to see a segment of ~100 points, but gnuplot had to load the entire file to produce the plot and it took a few seconds. ... I had to review hundreds of these short intervals, so I wrote a Perl script to load the data into memory and then present a prompt to accept commands as a front-end for gnuplot. ...
    (comp.graphics.apps.gnuplot)
  • Pen-Plot Track as Continuous Line?? Protel 99SE
    ... I'm trying to plot on copper to make circuit boards. ... Protel outputs Gerber. ... plotter. ... If line segments are plotted ...
    (sci.electronics.cad)
  • Re: Looking for a visualization tool for a data set
    ... segments alternating with 'stop' segments. ... Essentially I build a square wave plot out of it, ... mark saying it can't read the data file or some such. ... Gnuplot "code" reminds me of mathematica code.. ...
    (comp.graphics.apps.gnuplot)