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Matt J


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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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Answered
Discrepancy in sparse matrix math, when NaN's present
The response I seem to be getting from Tech Support is that this is expected behavior. NaNs are not guaranteed to propagate the ...

ungefär 8 timmar ago | 0

| accepted

Answered
Numerical Integrators With Problem-Based Optimization
but quickly realized that the class of variables used in the problem-based approach will not work with ode45 (or any root-findin...

en dag ago | 1

| accepted

Question


Discrepancy in sparse matrix math, when NaN's present
I expect result1 and result2 below to be identical, but they aren't. The discrepancy must be a bug, right? I'm working in R2024b...

3 dagar ago | 1 answer | 0

1

answer

Answered
Create a 2D image based on what a camera would see
You could just do a surface plot of the object, set the camera position parameters of the axes, and then use exportgraphics (whi...

5 dagar ago | 0

Answered
Assigning different data types to struct arrays using comma separated list assignment. Are there better options?
I like the performance of the code, however, I find it more difficult to read than for-loops Why not just use for-loops then, i...

5 dagar ago | 0

| accepted

Answered
I am getting the following error
There are many ways to generate that error. One of them is that you may be using 'end' as the name of a variable, e.g., end=1

7 dagar ago | 0

Answered
How to extract a specific frame from a video based on user input?
This example looks applicable to you: Read Video Frames Starting at Specific Time.

8 dagar ago | 0

Answered
Why do Nan values greatly increase the cost of sparse multiplication
I think you should report it as a bug. If you need a workaround, though, the following equivalent operation, which avoids implic...

8 dagar ago | 0

| accepted

Answered
How can I execute a function if it exist, otherwise use a custom function?
Have the used append (i.e., not prepend) your knnsearch to the path. If a native knnsearch exists above it in the path, it will ...

12 dagar ago | 0

| accepted

Answered
how to create a volume from the revolution of a variable area trapezoid
Here's a little bit more of a polished version of my original answer, which also generates a movie of the trapezoidal cross-sect...

13 dagar ago | 3

Answered
how to create a volume from the revolution of a variable area trapezoid
Along the lines of what @Mathieu NOE commented, I think it does make more sense to start with an elliptic cylinder and clip off ...

13 dagar ago | 3

Answered
Efficiently assign data into a struct?
You can replace all occurences of '1:end' with ':' and condense your indexing operations. This, for example, T1.var4.y = zer...

14 dagar ago | 0

Answered
How to multiply different size arrays and multiply each element by each element?
Download ndgridVecs from the File Exhange, https://www.mathworks.com/matlabcentral/fileexchange/74956-ndgridvecs?s_tid=srchtitl...

14 dagar ago | 0

Answered
Error using trainnet (line 46)
It appears that if your XTrain is in cell array form, you need to put your TTrain data in cell form as well: load('attachedData...

15 dagar ago | 1

| accepted

Answered
Indexing a 4-D array using a logical matrix
Assuming you are trying to extract the polygon interiors, you could do, [~,~,p,q]=size(map); Map=reshape(map,[],p*q); tes...

17 dagar ago | 0

| accepted

Answered
What is the difference between different ways to do least square
The train_100 system is underdetermined, so of course you aren't going to get a unique solution. For the 5k data, the only rea...

18 dagar ago | 1

| accepted

Answered
How to change the ratio of sectors for a circle with 8 equal sectors
One possibility: dTheta=360/8; %sector angle t=linspace(0,dTheta)'; sector=polyshape([0,0;cosd(t),sind(t)]); circle=array...

20 dagar ago | 0

| accepted

Answered
How to convert trajectory of the current vector to grayscale.
Maybe this is what you wanted? load("data.mat") Ia = data(:,1); Ib = data(:,2); Ic = data(:,3); %% Clarke (3 phase → αβ...

22 dagar ago | 1

| accepted

Answered
optimization optimplot capture frame
optimplot does not plot in a figure container of the type that you can get a handle to. Prior to R2025, you could probably have...

23 dagar ago | 0

| accepted

Answered
Preconditioning in fmincon
EDIT: You cannot pass a preconditioner on its own, nor would you want to if the true Hessian can be computed. However, using eit...

26 dagar ago | 0

Answered
How can I fit data to a piecewise function, where the breakpoint of the function is also a parameter to be optimised?
Why ? Both parabola can intersect below their respective maxima, and nonetheless the point of intersection can be the maximum y-...

30 dagar ago | 0

Answered
How can I fit data to a piecewise function, where the breakpoint of the function is also a parameter to be optimised?
Once you've chosen the coefficients of the first parabola [a1,b1,c1], the breakpoint is determined from, d=-b1/(2*a1) Only the...

ungefär en månad ago | 0

| accepted

Answered
suprisingly complicated optimization problem
This is another suggested strategy: to find the minimum possible qmax, given L. This seems at the very least like an important f...

ungefär en månad ago | 1

Answered
suprisingly complicated optimization problem
The motivation of this problem is the creation of the so called, "homogenized" 1-D grid, where consecutive distances between ele...

ungefär en månad ago | 0

Answered
suprisingly complicated optimization problem
Here's another formulation, closer to your original one. It uses fmincon and is really fast (when the problem is feasible), but ...

ungefär en månad ago | 1

Answered
suprisingly complicated optimization problem
My thought is that you, (1) Do not include L in your list of unknowns. Solve a series of optimization problems for fixed L=1,2,...

ungefär en månad ago | 2

Answered
How to check whether a name is a locally accessible function?
One way, function tf = top_level_function(name) s=functions(str2func(name)); tf=strcmp( s.type , "scopedfunction") ...

ungefär en månad ago | 0

| accepted

Answered
how to find orthonormal vector with condition?
n=[0,null([y,z])']

ungefär en månad ago | 0

Answered
Error `Index exceeds the number of array elements` while loading .mat file
You have created a variable named 'load' in this line, load = 0; % 轴承的载荷(单位:马力)(可能是0、1、2、3马力) and later also in,...

ungefär en månad ago | 1

Answered
AppDesigner: Is it possible to interactively stretch/schrink plots ("Axes") in x or y direction separately (NOT zoom in/out both)?
This example looks applicable to you: Restrict Zooming to X-Dimension.

ungefär en månad ago | 0

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