finding 2D curvature for a left ventricular plot

> load('D:\Matlab\315 Big.txt');
 Vertices=[sin(r) cos(r)]*10;
Lines=[(1:size(Vertices,1))' (2:size(Vertices,1)+1)']; Lines(end,2)=1;
Na=zeros(size(Vertices,1),1); Nb=zeros(size(Vertices,1),1);
Na(Lines(:,1))=Lines(:,2); Nb(Lines(:,2))=Lines(:,1);
checkNa=Na==0;
checkNb=Nb==0;
Naa=Na;
Nbb=Nb;
Naa(checkNa)=find(checkNa);
Nbb(checkNb)=find(checkNb);
Na(checkNa)=Nbb(Nbb(checkNa));
Nb(checkNb)=Naa(Naa(checkNb));
Ta=-sqrt(sum((Vertices-Vertices(Na,:)).^2,2));
Tb=sqrt(sum((Vertices-Vertices(Nb,:)).^2,2)); 
Ta(checkNa)=-Ta(checkNa);
Tb(checkNb)=-Tb(checkNb);
x = [Vertices(Na,1) Vertices(:,1) Vertices(Nb,1)];
y = [Vertices(Na,2) Vertices(:,2) Vertices(Nb,2)];
M = [ones(size(Tb)) -Ta Ta.^2 ones(size(Tb)) zeros(size(Tb)) zeros(size(Tb)) ones(size(Tb)) -Tb Tb.^2]; 
invM=M.^-1;
a(:,1)=invM(:,1,1).*x(:,1)+invM(:,2,1).*x(:,2)+invM(:,3,1).*x(:,3);
a(:,2)=invM(:,1,2).*x(:,1)+invM(:,2,2).*x(:,2)+invM(:,3,2).*x(:,3);
_Index in position 3 exceeds array bounds (must not exceed 1)._

[phuah yun]

im trying to get the curvature but i have no idea which codes to use.. rather challenging task when i have no basics of matlab at all

[madhan ravi]

select the whole code and press the code button {} so that its easy to read and upload Big.txt file to test

[phuah yun]

a(:,2)=invM(:,1,2).*x(:,1)+invM(:,2,2).*x(:,2)+invM(:,3,2).*x(:,3);

at this part it prompts (Index in position 3 exceeds array bounds (must not exceed 1).) is there any problem with this line?

[madhan ravi]

did you read my previous comment??

[phuah yun]

yes, i have no idea how to do that..

[Image Analyst]

Edit your question, the click the paper click icon above the edit box.

[madhan ravi]

don't close question which has answers

Answer 1

[KSSV]

Refer this: https://in.mathworks.com/matlabcentral/fileexchange/32696-2d-line-curvature-and-normals

[KSSV]

       Vertices =load(''D:\Matlab\315 Big.txt');
      Vertices(:,1) = [] ;   % because all zeros     
      k=LineCurvature2D(Vertices) ;

Use the attached code as it is.....

Note that this is a function written by other guy. You need to rate it at the respective link.

Answer 2

[madhan ravi]

 M =load('D:\Matlab\315 Big.txt');
  r=4;
   Vertices=[sin(r) cos(r)]*10;
  Lines=[(1:size(Vertices,1))' (2:size(Vertices,1)+1)']; Lines(end,2)=1;
  Na=zeros(size(Vertices,1),1); Nb=zeros(size(Vertices,1),1);
  Na(Lines(:,1))=Lines(:,2); Nb(Lines(:,2))=Lines(:,1);
  checkNa=Na==0;
  checkNb=Nb==0;
  Naa=Na;
  Nbb=Nb;
  Naa(checkNa)=find(checkNa);
  Nbb(checkNb)=find(checkNb);
  Na(checkNa)=Nbb(Nbb(checkNa));
  Nb(checkNb)=Naa(Naa(checkNb));
  Ta=-sqrt(sum((Vertices-Vertices(Na,:)).^2,2));
  Tb=sqrt(sum((Vertices-Vertices(Nb,:)).^2,2)); 
  Ta(checkNa)=-Ta(checkNa);
  Tb(checkNb)=-Tb(checkNb);
  x = [Vertices(Na,1) Vertices(:,1) Vertices(Nb,1)];
  y = [Vertices(Na,2) Vertices(:,2) Vertices(Nb,2)];
  M = [ones(size(Tb)) -Ta Ta.^2 ones(size(Tb)) zeros(size(Tb)) zeros(size(Tb)) ones(size(Tb)) -Tb Tb.^2]; 
  invM=M.^-1;
  a(:,1)=invM.*x(1)+invM.*x(2)+invM.*x(3);

[madhan ravi]

if it doesn't work upload your text file by clicking the paperclip button

[phuah yun]

This is the txt file. thanks so much

[madhan ravi]

check edited answer

[phuah yun]

it says that the matrix size is different on the left and right. The code used was from the link KSSV provided just now same link but stuck.

[KSSV]

What made you to change the function? You can straight away use the function eh.

[phuah yun]

the inverse M had an error code saying its undefined following by:a(:,2)=invM(:,1,2).*x(:,1)+invM(:,2,2).*x(:,2)+invM(:,3,2).*x(:,3); this having a error code: Index in position 3 exceeds array bounds (must not exceed 1).

[KSSV]

Clearly int he function invM is a 3D matrix..where as in your case it is not.....so the error. My question is what is stopping you to use the function with out changes? Why did you change it?

[phuah yun]

i changed the function cos there is an error code.

[KSSV]

That case..you have to show us what error you got.

Answer 3

[Bruno Luong]

The original code is here:

FEX exchange

Sorry but you you don't master the MATH behind, why wasting your time (and our time) to make your horrible modifications?

The way you compute the inverse the matrix tells clearly that you don't have a math background to make any modification.

[phuah yun]

yes i know nothing about this. trying to figure out. i used the original code, and got this error: function k=LineCurvature2D(Vertices,Lines) ↑ Error: Function definition not supported in this context. Create functions in code file.

[Bruno Luong]

If you don't know how to download a FEX and how to use/call it then please ask question in this sense rather than trying to make modification on the code (again it beyond what your level of MATLAB) and ask why it doesn't work.

[phuah yun]

would you be able to provide any assisstance in this case where the error code show: function k=LineCurvature2D(Vertices,Lines) ↑ Error: Function definition not supported in this context. Create functions in code file.

[Bruno Luong]

Easy, just do what the message tells you "Create functions in code file."

Or you downnload the FEX zip file and unzip it in the working folder, and call it correctly, and not copy past the code in your script.

[phuah yun]

how do i create functions in code file in this case? the function that i am supposed to code is this? (k=LineCurvature2D(Vertices,Lines))

[Bruno Luong]

I just told you Downnload the FEX zip file and unzip it in the working folder

[phuah yun]

im sorry but where is the working folder? i downloaded it, and opened it opened in the editor window. i started with M =load('D:\Matlab\315 Big.txt'); then followed by the code is that okay?

[Bruno Luong]

Sorry I don't have time to help you. Please post question in separate thread might be someone else is able to help you with basic function calling or read the Matlab Starting Guide.