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Matt J


5,428 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

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Answered
Generating a matrix based on an equation with conditions
For example, >> A=zeros(10,1); A(1:5)=4; A(6:10)=3 A = 4 4 4 4 4 3 3 3 ...

19 hours ago | 1

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Answered
Create an accurate boundary around 2D point cloud horizontal plane
You can use alphaShape.

21 hours ago | 0

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Interpolating a 3D Matrix using interp1
Using my KronProd class (Download) m=14; p=221; A = rand(m,m,p) ; M=40; %new XY dimension B=interp1(eye(m),linspace(1,m,M),...

1 day ago | 0

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Can I use Optimization tool like fmincon or ga etc if I have constraint optimization problem that optimization variable cannot be within a range inside upper and lower limit?
Example : suppose I am solving an optimization problem where x should be within 1 and 10 or 29 and 99. The feasible space for x...

1 day ago | 0

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Finding a pixel location after imrotate
Well, the center of the image in your example is at c=[512.5;340]; and the rotation matrix expressing the rotation is R=[cosd...

1 day ago | 1

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Adding constraints to lsq fitting
Any chance you could modify the code without the weighting function and with the new data? Note that this means rdf_contact and ...

2 days ago | 0

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Adding constraints to lsq fitting
Here is an adaptation of the algebraic solution that I presented in your previous thread. I don't bother with the lsqcurvefit a...

3 days ago | 2

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initlalize several variables at once
Just to sum things up here, below is my implementation of the fit, combining all my various recommendations. Both the algebraic ...

3 days ago | 0

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initlalize several variables at once
One other thing I would point out is the model function you have shown us here is linear in the coefficients. This means that it...

3 days ago | 1

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How to automatically constrain some of the unknown values in an optimization problem?
I will assume you have some binary vector v which indicates the groupings of the variables, so for example this, [0 0 x(1) x(2)...

3 days ago | 1

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initlalize several variables at once
Is there a way to more easily set this, assuming they all have the same initial guess? One way: params0=linspace(0.1,0.1,13) ...

4 days ago | 1

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initlalize several variables at once
If all you're trying to do is polynomial surface fits of various orders, I would just use the Curve Fitting Toolbox, if you have...

4 days ago | 1

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Answered
Replace part of matrix with other matrix.
Z=zeros(2); B=B+cell2mat({Z,A,A1;A2,Z,A3;A,A1,Z})

4 days ago | 1

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Answered
General Approach to Fitting dozens of curves using the same coefficients
You can use lsqcurvefit to do so, simply by posing the problem as a 30-parameter fit. If you do this, you will want to provide a...

5 days ago | 1

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Answered
merge non-intersecting polygons
Use bwconvhull.

5 days ago | 0

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Placing values in a matrix with values from another matrix
A(A==1)=B;

5 days ago | 0

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Number of elements error
for i = 3:(length(x)-2) ff(i) = (-1*x(i+2)+6*x(i+1)-3*x(i)-2*x(i-1))/(6*dx); L = L + dx*((f(x(...

5 days ago | 0

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Removing sub matrix from 3d matrix, if any values in the matrix exceed a certain min/max value
discard=any( any( epochs_CG(1:2, :, :)>=100 ,2) ,1); epochs_CG(:,:,discard)=[];

5 days ago | 0

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Answered
How to replace 2x2 zero sub matrices by different 2x2 matrices ?
basically i want solution in this form x p1 p2 p3 p1 x p2 p3 p1 p2 x p3 p1 p2 p3 x C={zeros(2), p1,p2,p3}; result=B+ce...

5 days ago | 0

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Answered
How to replace 2x2 zero sub matrices by different 2x2 matrices ?
Here is a simple example, but the right hand side can be any array with an appropriate number of elements B(B==0)=1:48;

5 days ago | 0

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Plotting subplot with two concurrent plots
figure; for k = 1:5 subplot(2,5,k); [val,loca]=(max(abs(squeeze(S(1,k,:,:))))); plot(T,squeeze(abs(S(1,k,92,:))),T,squeeze...

5 days ago | 0

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Answered
How to use blkdiag command to create a matrix such that its diagonal blocks are random 2 x 2 matrices?
Acell=mat2cell(rand(8,2), ones(1,4)*2,2) B=blkdiag(Acell{:})

5 days ago | 0

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Answered
Not quite fitting the data using lsqcurvefit
When your model function is fully vectorized, as suggested by Walter, the results are better, but only you can know for sure wha...

6 days ago | 0

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Defining array contents - order doesn't matter - Linear programming problem
It does not matter what order the B(i) are in, as long as the ordering of the rows A(i,;) matches B(i).

8 days ago | 0

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How to split array in n part every m points ?
I don't know of any built-in function that will do that, but it is easy to implement: function B=foo(A,p,r) N=numel(A); ...

8 days ago | 2

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Hgtransform and makehgtform at fsurf
If the cone has the orientation you want, but not the location , you can add a translation to put it where you want, set(t,'Mat...

8 days ago | 0

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How do I use a AVERAGEIFS statement of excel within a range for multiple data of irregular intervals in matlab?
Something like this would do it, groups=discretize(altitudes,ranges); averages=splitapply(@mean, temperature,groups);

8 days ago | 0

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How to write a matrix using for loop
Yes.

9 days ago | 2

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Improving LSQCcurvefit solutions through improving x0 through loops
I can see that your model function derives in some way from the quadratic formula, but I can't quite see where all the pieces ar...

10 days ago | 0

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