# Math Help - Matlab - Shortest Distance

1. ## Matlab - Shortest Distance

I have just started to use matlab and I am trying to find the shortest distance from a point P=(8,20) to a plane: v(a,b) = [6,0,0] + a[-2,1-0] + b[-1,0,1]
So far all I have done is to find the normal vector.
I know how to do this normally just unsure in matlab - any help would be great.

Thanks

2. Originally Posted by metafolic
I have just started to use matlab and I am trying to find the shortest distance from a point P=(8,20) to a plane: v(a,b) = [6,0,0] + a[-2,1-0] + b[-1,0,1]
So far all I have done is to find the normal vector.
I know how to do this normally just unsure in matlab - any help would be great.

Thanks
You might try something like this:

Code:
%  NOTES
%  x*y' is the inner product or dot product of x and y
%

p=[8,2,0];
cc=[6,0,0];
v1=[-2,1,0];
v2=[-1,0,1];

p=p-cc;  %translate everything so plane goes through origin

u1=v1/sqrt(v1*v1');  %gramm-schmitt orthogonalisation of v1 and v2
u2=v2-(u1*v2')*u1;
u2=u2/sqrt(u2*u2');

dd=p-(p*u1')*u1-(p*u2')*u2;     %get component of p normal to the u1, u2 plane

dist=sqrt(dd*dd'); distance of p from the plane
But I have not checked this as I don't have Matlab or Octave on this machine.

RonL

3. ## Massey 160.102 huh...

same problem..except i dont even know how to find the normal vector

4. Originally Posted by deragon999
same problem..except i dont even know how to find the normal vector
Perhaps if you looked at the detail of the proposed code, that might help.

RonL