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Matt J


Last seen: Today
6,456 2009 年以降の合計貢献数

Professional Interests: medical image processing, optimization algorithms

PLEASE NOTE: I do not read email sent through my author page. Please post questions about FEX submissions in their respective Comments section.

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I want to rotate a point using Quaternion function
You could also try this FEX submission instead of the Quaternion class https://www.mathworks.com/matlabcentral/fileexchange/308...

約7時間 前 | 0

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Faster alternative to mode?
It would be better not to implement the mode calculation repeatedly in a loop over the voxels. If you have enough RAM to hold 27...

約7時間 前 | 0

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I want to rotate a point using Quaternion function
q1*[1;2;3]

約7時間 前 | 0

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Extracting indices from 3D matrix for another 3D matrix
[m,n,p]=size(A); [~,J,K]=ndgrid(1:m,1:n,1:p); idx=sub2ind([m,n,p],I,J,K); A(idx)./B(idx)

約7時間 前 | 0

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Number of sequences with 3 or more ascending numbers
all( diff(v(k:k+2)) >= 0 )

約7時間 前 | 0

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how to find the angle between 2 points ?
atan2d(y2-y1,x2-x1);

約7時間 前 | 0

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Solving nonlinear equation using newton-raphson method
i=0; del = Inf; while del > tol && i<N i=i+1; f(i) = 3*P*V(i).^3 - P*V(i).^2 + 9*V(i) - 8*...

2日 前 | 1

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Creating a multi-dimensional array out of many lower-dimensional arrays
If your "datasets" really are in the form of the Matlab dataset type described here, then I think you could probably just do som...

2日 前 | 0

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Cells and Cell vectors help?
So, as a smaller example, if n=4 and the input is this C={ [1 2] , [], [2 3 4], [] }, the output should be this, A = 1...

3日 前 | 0

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How to calculate from three points the "normal" at the second point
Once you have answered David's question, the attached function should be useful. It will find the normals to all the facets of a...

4日 前 | 1

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Using Groups of Rows in a Parfor Loop
As mentioned in my comment, your example does not make it clear why a loop is necessary at all. However, the reason for your dif...

5日 前 | 0

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Help with non working for loop for generating a matrix
One approach is to write x,y, and A as matrix-valued anonymous functions of c, e.g., x=@(c)(4-c)./(6+c); y=@(c)10./(6+c); ...

7日 前 | 0

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Quadratically constrained linear maximisation problem: issues with fmincon
Well, it would be interesting to know what algorithm Gurobi uses, but the issue of the objective function difference appears to ...

7日 前 | 0

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How can I create random Co-ordinate shifts (x,y,z) that add to a displacement of 1?
[a,b,c]=sph2cart(2*pi*rand,pi*rand,1);

7日 前 | 0

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How to constrain distance between points in optimization?
It can be set up this way, but keep in mind that this is a highly non-convex feasible set. It may be challenging to find a glob...

8日 前 | 1

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Multidimensional operations without for loop
Q=nan(8,n); [J,K]=ndgrid(1:8,1:n); I=maxloc(K); thetaIndices=sub2ind(size(theta), I,J,K); QIndices=sub2ind(...

10日 前 | 0

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fzero with function in matrix
syms x a=[sin(x),1;1,1]; b=[1/cos(x);1]; c=a*b; x=fzero( matlabFunction(c(1)-1) , pi/4 )

11日 前 | 0

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How can i speed up my code?
Please do not provide code in the form of embedded images. It prevents us from conveniently copy/pasting relevant sections. In ...

11日 前 | 0

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Get the diagonal without calculating the explicit matrix
Assuming B*C results in a square matrix, diagonal=sum(B.' .* C, 1);

12日 前 | 1

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Finding Area of Polygon defined by roipoly
roipoly returns a logical mask BW of the region BW = roipoly; so, its area in whole pixels would simply be area = sum(BW(:));...

12日 前 | 2

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Setting nonlcon for fmincon / patternsearch as a matlabfunction
Create a wrapper function like the one below. To make it visible from the workspace where patternsearch is called, you can make ...

12日 前 | 1

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Use of kron with more than two matricies
One way would be to use my KronProd class https://www.mathworks.com/matlabcentral/fileexchange/25969-efficient-object-oriented-...

12日 前 | 1

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How to find a minimal number of rows in a sparse matrix to form a square sub-matrix for a given row?
If you have the Optimization Toolbox, you can try this linear programming solution: A = [ -1 1 0 0 0 0 ...

15日 前 | 0

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How to plot a single variable function with constraints
You can assign NaN to anything you don't want plotted. Example, x=linspace(0,2,1000); f=sin(x); f( 0.5<=x & x<=1)=nan; p...

17日 前 | 0

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How to quickly find the column index of the last non-zero element in all rows in a sparse matrix?
[~,idx]=max(fliplr(logical(A)),[],2); result=size(A,2)+1-idx;

18日 前 | 0

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Create n equidistant point along a circle
theta=linspace(0,360,n+1); theta(end)=[]; x=R*cosd(theta)+x0; y=R*sind(theta)+y0;

18日 前 | 0

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polyfit curve turns around near last point
Your data, when plotted alone, do not look very polynomial like. They do not even look like a function. x = [0 0 -0.0063 -0...

19日 前 | 0

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How to quickly find the first non-zero element without iterations in all columns in a sparse matrix?
See this FEX submission, https://www.mathworks.com/matlabcentral/fileexchange/24641-vectorized-find-with-first-option

19日 前 | 0

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How to quickly find the first non-zero element without iterations in all columns in a sparse matrix?
[~,result]=max(logical(A),[],1);

19日 前 | 0

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Use fsolve with an elliptic integral
It does not make sense to have a relational expression like, [K, E]== ellipke(m) as one of your equations, expecially one that...

20日 前 | 0

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