Principal axis of moment of inertia-error in code

I am calculating the pricipal axis using moment of inertia.

In the code I use (Not written by me, I am a beginner) I get following error. Only the first part attached.

Thanks very much

Operator '+' is not supported for operands of type 'struct'.

Error in mass (line 15)

connection = connection + (1);

function [Centroid,SurfaceArea,Volume,CoM_ev123,CoM_eigenvectors,I1,I2,I_CoM,I_origin,patches] = mass(varargin)

if (nargin == 0)

[ivFile,filepath] = uigetfile('*.stl','SELECT FILE');

varargin{1} = fullfile(filepath, ivFile);

end

if (nargin==2 && ischar(varargin{1}) && ischar(varargin{2}))

varargin{1} = fullfile(varargin{1},varargin{2});

end

if (ischar(varargin{1}))

[points, connection] = read_vrml(varargin{1});

connection(:,1) = [];

connection = connection + 1;

elseif (nargin==2 && isnumeric(varargin{1}) && isnumeric(varargin{2}) && size(varargin{1},2)==3 && size(varargin{2},2)>=3)

points = varargin{1};

connection = varargin{2};

if (size(connection,2)==4)

connection(:,4)= [];

end

if (min(min(connection))==0)

warning('MassProperties:ConnIndex','Connection matrix appears to be still 0-indexed, adding 1 to all indices');

connection = connection + 1;

end

else

error('MassProperties:Arugments', 'No ivFile or pts & conn were passed in');

end

[Samyuktha]

Hi Mel,

You're getting the following error as 'read_vrml' reads a VRML 1.0 file into a MATLAB structure and hence, connection is of the datatype 'struct'.

More details about 'read_vrml' can be found in the documentation link : read_vrml