Transpose on ND array is not defined.

somebody could help me with this message ???

Transpose on ND array is not defined.

I tried to use the function inhull(testpts,K,tess) but I can't! ??? Error using ==> inhull at 67 testpts and xyz must have the same number of columns

>> size(K)

ans =

        1452           3

>> size(testpts)

ans =

    32     8    66

[Jan]

What is the error message: "Transpose on ND..." or "testpts and xyz must have..."?

[david Fernandez]

the question is how i could solve the problem of using inhull with the testpts and K as a variables, how I can manage to have the same dimension?

Answer 1

[Jan]

If you are working with John D'Errico's INHULL, the documentation in the FEX seems to tell, that you need 2D matrices as input. Why is your textpts a 3D array?

[david Fernandez]

yes, I'm using John D'Errico's inhull, but it says:

arguments: (input)

% testpts - nxp array to test, n data points, in p dimensions

% If you have many points to test, it is most efficient to

% call this function once with the entire set.

%

% xyz - mxp array of vertices of the convex hull, as used by

% convhulln.

%

% tess - tessellation (or triangulation) generated by convhulln

% If tess is left empty or not supplied, then it will be

% generated.

It works for any 'd' dimension, no ?

I create my testpts as: testpts=[xMat, yMat, zMat]

K=convhulln(V);

V are the vertices of my triangulated mesh of the image in file.stl binary

[Walter Roberson]

No, it doesn't work for any 'd' dimension. When you are working with a points in higher-dimension space, it is common to represent them as 2D matrix, one row per point, and then the number of columns corresponds to the dimensionality of the points.

Answer 2

[Walter Roberson]

Transpose is only defined for 2D arrays. For arrays of higher dimension, permute() must be used.

If you are working with an image, you have probably inadvertently used a truecolor (RGB) image in a context that needs a binary or grayscale image.

[david Fernandez]

I tried to permute but it didn't work and I'm working with a binary 'stl' file.

Any idea how to solve it ?

[Jan]

Please show what you've tried exactly and add the error message.

[david Fernandez]

i'm trying to find the skeleton of an image in stl file (binary).

The code I use is:

%Read the binari STL file

[F,V,N] = STLREAD('FILENAME'); % returns faces F, vertices V and the face normal vectors N separately

%create 3D binary box

bboxPts=[min(V,[],1);max(V,[],1)];

bboxDiff=ceil(diff(bboxPts));

%subdivision of the space box

xVec=linspace(bboxPts(1,1),bboxPts(2,1),2*bboxDiff(1));

yVec=linspace(bboxPts(1,2),bboxPts(2,2),2*bboxDiff(2));

zVec=linspace(bboxPts(1,3),bboxPts(2,3),2*bboxDiff(3));

[xMat,yMat,zMat]=meshgrid(xVec,yVec,zVec);

normals=N;

%convex hull

K=convhulln(V);

trisurf(K,V(:,1),V(:,2),V(:,3));

%call inhull, return if is inside or not

X =[xMat;yMat;zMat]; %option1

testpts=permute(X,[2 3 1]);

%testpts=[xMat';yMat';zMat']; %option 2

tess=trisurf(K,V(:,1),V(:,2),V(:,3));

in = inhull(testpts,K,tess);

image3D = reshape(in,size(xMat));

%Calculate Skeleton

edtImage3D=bwdist(~image3D);

labeledImage = watershed(edtImage3D);

unique(labeledImage(:)) %ans = 1

[Walter Roberson]

X = [xMat(:), yMat(:), zMat(:)]