Thread Subject:

function in nlinfit

Hi
i am trying to compute a cylinder from a Point Cloud. I approximated starting Values and with them i want to use nlinfit to get my 7 parameters for a cylinder( x,y,z for 1 Point on the axis, x,y,z for axis direction and the radius ).
I wrote following function :
function [ Mx,My,Mz,ax,ay,az,r,resi ] = computeCylinder(X, Mx0,My0,Mz0, ax0,ay0,az0,r0 )
%COMPUTECYLINDER Summary of this function goes here
% Detailed explanation goes here
    y = zeros(length(X),1);
    cyl = @(a,x)((a(2)*(a(6)-x(3))-a(3)*(a(5)-x(2)))^2
                   + (a(3)*(a(4)-x(1))-a(1)*(a(6)-x(3)))^2
                   + (a(1)*(a(5)-x(2))-a(2)*(a(4)-x(1)))^2
                     - a(7)*sqrt((a(1))^2+(a(2))^2+(a(3))^2));
    a0 = [Mx0,My0,Mz0,ax0,ay0,az0,r0];
    [aComp, resi] = nlinfit(X,y,cyl,a0);
    Mx= aComp(4);
    My= aComp(5);
    Mz= aComp(6);
    ax= aComp(1);
    ay= aComp(2);
    az= aComp(3);
    r = aComp(7);

end

X is my PointCloud ( dimension is 115568x3). The other input Parameters are the starting values.

When i run this function i get the following error :
Error using nlinfit (line 126)
MODELFUN must be a function that returns a vector of fitted values the same size as Y (115568-by-1). The model
function you provided returned a result that was 1-by-1.

One common reason for a size mismatch is using matrix operators (*, /, ^) in your function instead of the
corresponding elementwise operators (.*, ./, .^).

On 22 Mai, 08:44, "Jan " <hack...@gmail.com> wrote:
> Hi
> i am trying to compute a cylinder from a Point Cloud. I approximated starting Values and with them i want to use nlinfit to get my 7 parameters for a cylinder( x,y,z for 1 Point on the axis, x,y,z for axis direction and the radius ).
> I wrote following function :
> function [ Mx,My,Mz,ax,ay,az,r,resi ] = computeCylinder(X, Mx0,My0,Mz0, ax0,ay0,az0,r0 )
> %COMPUTECYLINDER Summary of this function goes here
> %