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Matt J


Last seen: Today
7,993 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

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Answered
Fitting cone/cylinder of known dimensions to 3D surface data
I've recently added a cone-fitting routine to this FIle Exchange package, https://www.mathworks.com/matlabcentral/fileexchange/...

8 hours ago | 0

Submitted


Object-oriented tools for fitting conics and quadrics
A tool set for fitting various conics and quadric surfaces, e.g., ellipses, cylinders, spheres, planes, cones, and lines.

8 hours ago | 13 downloads |

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Answered
Optimization least square approach
Shouldn't it be err = sum (real(error).^2) + sum(imag(error).^2) ; If so, then this is a linear least squares problem, and you...

14 hours ago | 0

Answered
Fitting cone/cylinder of known dimensions to 3D surface data
I am providing a guess that is not too far from the original values. If so, it sounds like there is an error in your calculatio...

1 day ago | 0

Answered
Reducing every value of a matrice every time by the same value
This might be what you want, but as @Scott MacKenzie says you've left a lot of problem details and issues for us to guess, whil...

2 days ago | 0

Answered
Problem structure with LSQNONLIN set in optimoptions object still uses FMINCON
I don't think you can use the optimvar framework to launch lsqnonlin, because lsqnonlin does not take a scalar objective. You wi...

2 days ago | 0

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Answered
How to extract the Jacobian matrix from the given equation?
If EX and EY are positive definite, one solution is simply, J=chol(EY).'/chol(EX).' In general, there won't be a unique soluti...

2 days ago | 1

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Answered
Optimization problem with quadratic function
You can use isosurface() to plot and quadprog() to minimize.

2 days ago | 0

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Answered
anyway to find common tangent for two functions
The problem has 6 unknowns, the (xc,yc) coordinates of the circle center and the (x,y) coordinates of each point of tangency. Ea...

3 days ago | 0

Answered
how can we compare two columns for a particular value of another column?
Say A is the matrix of values. [~,uniqueRows]=unique(A(:,[1,4,5]),'rows') This will tell you which rows can be kept so as to ...

3 days ago | 0

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Answered
Can the matrix be displayed in a way other than imagesc, imshow, image or pcolor commands (similar to the plot command)?
One possibility is to use pgonCorners (which must be Downloaded) https://www.mathworks.com/matlabcentral/fileexchange/74181-fin...

3 days ago | 0

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Answered
Submatrix sum (but just on a section)
You can use sepblockfun (Download) A=rand(4914); B1=sepblockfun(A,[189,1],'sum'); %the results B2=sepblockfun(A,[1,189],'su...

5 days ago | 0

Answered
How can I change for-loop into matrix way?
This gives some speed-up. %Fake Data m=100;n=1000; B=rand(15,1); D=rand(3,1); A=B(randi(15,m+1,n)); E=D(randi(3,m+1,1))...

5 days ago | 0

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Answered
How to check whether multiple variables are numeric using a loop
varname=D_mat_search(aa); if exist(varname,'var') && isnumeric(eval(varname)) && isfile(File_loc_ID) %BAD

5 days ago | 0

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Answered
OOP: Reference (subclass) enumeration names from static superclass method. Possible?
No, you can't unfortunately, but you can avoid copying the method to all the sub-classdef's just by making doWork() an external ...

5 days ago | 1

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Answered
How to fill a volume plot of a vector valued functions (with 3 variables)
See quiver3. https://www.mathworks.com/help/matlab/ref/quiver3.html

5 days ago | 0

Answered
How to find the polynomial equation when factors is provided?
p = poly([-7,19,18,-17])

5 days ago | 1

Answered
Percentile calculation along time
T=cat(3,A,B,C,D,E) ; prctile( T ,50,3 )

6 days ago | 0

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Answered
Help: Using fminsearch to calculate fractional derivatives
Your optimization problem appears to be an unconstrained, linear least squares minimization. I don't see why you need an iterati...

6 days ago | 0

Answered
Angle of lines in binary image
It may be helpful to use linear2dFit from this FIle Exchange package https://www.mathworks.com/matlabcentral/fileexchange/87584...

6 days ago | 0

Answered
Fitting exponential curve in data
A more efficient and direct way would be to use fminspleas (Download) load data funlist={@(tau,t)exp(-t/tau),1}; idx=tdat...

6 days ago | 0

Answered
How to plot 2 lines and find the coordinates of their intersection?
Using this File Exchange submission, https://www.mathworks.com/matlabcentral/fileexchange/93470-intersections-of-multiple-2d-li...

7 days ago | 0

Answered
How can I fit an ellipse in 3D space to find it's center coordinates in (x,y,z)?
Basically, the procedure would be to Fit a plane to your data. Project your (x,y,z) data on to the plane and write the resul...

7 days ago | 2

| accepted

Answered
How to get the max orthogonal (perpendicular) distances from a set of coordinates
I created an alternative to polyxpoly here, https://www.mathworks.com/matlabcentral/fileexchange/93470-intersections-of-multipl...

9 days ago | 1

Submitted


Intersections of multiple 2D lines or line segments
Compute the intersection of a reference line (or line segment) with a polyshape boundary or with a batch of other line segments....

9 days ago | 5 downloads |

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Answered
problem with VPASOLVE and FSOLVE
No, your equations don't have closed-form solutions. In any such situation, you will have to provide an accurate initial guess t...

10 days ago | 0

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Answered
3D matrix with equation
If it helps, I need to sum over index i afterwards, so this will reduce the dimensions again afterwards. Don't multiply-then-su...

10 days ago | 0

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Answered
Fmincon gives Exact the same Answer as the initial guess
Because of the round() operations, your objective function is locally flat (i.e., has zero gradient) almost everywhere. Therefor...

11 days ago | 1

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Answered
why hough transform detects more lines while there is only one line?
Because your line is actually not a line, but rather a tube with non-zero thickness, there are multiple thinner lines that will...

11 days ago | 0

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Answered
Create sperate matrices for all unique values in the 3rd column of a cell array
Well, I won't talk about creating separate arrays because it's bad, but here's what you could do which wouldn't be bad: initia...

11 days ago | 0

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