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Calculate matrix from symbolic equation

Asked by jnaumann on 19 Sep 2013

Hi everyone,

I have used the following code to generate a symbolic equation for a plane given 3 points.

P1=[1747 444 1051];
P2=[1771 115 1053];
P3=[9 290 66.05];
normal = cross(P1-P2, P1-P3);
syms x y z;
P = [x,y,z];
planefunction = dot(normal, P-P1);
dot(P-P1, normal);
realdot = @(u, v) u*transpose(v);
realdot(P-P1,normal);
zplane = solve(planefunction, z);

I would now like to generate an m x n matrix (3506 x 1057) using this equation but keep getting stuck. Does anyone know how to do this? I am sure it is very simple

Many thanks in advance

2 Comments

Azzi Abdelmalek on 19 Sep 2013

What exactly is your problem? is there any error message?

jnaumann on 19 Sep 2013

No, I haven't got to that stage yet. I have the equation describing the plane. I just don't know how to generate a matrix using that equation. Say I want to generate a 2D matrix where x=1:3000 and y=1:1000 for example, how can I do this?

Thanks

jnaumann

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1 Answer

Answer by Sean de Wolski on 19 Sep 2013
zp = subs(zplane,{x,y,z},{1:100,1:100,1:100})

To get a numeric solution from this:

double(zp)

1 Comment

jnaumann on 19 Sep 2013

Thanks for your quick response. I have tried the code you provided. Should this produce a matrix or vector since when I plot the answer I get a line. Is this expected and how to I change it to get a matrix(to plot a surface)?

Cheers

Sean de Wolski

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