# Matt J

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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**Feeds**

randomAffine3d is not properly random

EDITED: If you don't like what the default randomizer is doing, randomAffine3d() also let's you define your own, e.g., ori = [e...

4 hours ago | 0

randomAffine3d is not properly random

If you want an isotropic distribution across the entire sphere, this should do it. ori = [eye(3);-eye(3)]; N=1000; o=cell(N...

4 hours ago | 0

slow imwarp with large arrays

20k x 20k is an incredibly high resolution. Do you really need it, and if so, do you really need to use cubic interpolation, as ...

2 days ago | 0

Solved

Sum along each diagonal of a matrix

Write a routine that returns the sums along the diagonals of a given matrix, A, where the first diagonal is the bottom left corn...

2 days ago

Warning: Equation is badly conditioned. Remove repeated data points or try centering and scaling.

9th order polynomials do tend to be badly conditioned. Try using a lower order, or perhaps a spline model.

2 days ago | 0

help counting number of times a value occurs across matrix

values = [111, 112, 121, 122, 211, 212, 221, 222, 311, 312, 321, 322, 411, 412, 421, 422]; edges=[values,inf]; dp = [111 112...

3 days ago | 0

Problem

Sum along each diagonal of a matrix

Write a routine that returns the sums along the diagonals of a given matrix, A, where the first diagonal is the bottom left corn...

3 days ago | 0 | 9 solvers

Unable to achieve desired speed up using parfor

I find that all instances on B finish in about half the time as those on A. It baffles me... That is the expected result, assu...

7 days ago | 0

Solved

Sum All Positive Elements

Output a scalar that is equal to the sum of all positive elements in a given vector/matrix. For Example: The sum of all positi...

7 days ago

Solved

Build a block Toeplitz matrix

A symmetric block Toeplitz matrix has the form, where the are compatibly-sized matrices. Write a routi...

7 days ago

How to avoid unrecognized option names using optimget

Although I am using R2024a, that particular code still uses an older (2016-2019) version of lsqcurvefit. If so, problem solved....

7 days ago | 0

| accepted

Problem

Build a block Toeplitz matrix

A symmetric block Toeplitz matrix has the form, where the are compatibly-sized matrices. Write a routi...

7 days ago | 0 | 4 solvers

Finding the Center of Broken Vase Slices

You can use ellipticalFit() from this download, https://www.mathworks.com/matlabcentral/fileexchange/87584-object-oriented-tool...

7 days ago | 1

Problem

Condition number of Kronecker product

Given NxN matrix A and MxM matrix B, where M,N<=1000, write a routine to compute the condition number of kron(A,B).

7 days ago | 0 | 4 solvers

Solved

2x2 binning of a large sparse matrix

Consider the 20000 x 20000 sparse matrix, A=round(sprand(2e4,2e4,1/1e4*100)*1000); The task is to divide this matrix into 2x...

9 days ago

Solved

Convert a vector into numbers

Suppose a vector x = [ 1 2 4 7] is given. You have to convert this vector into string number y = '1247'. Examples x = [ 1...

10 days ago

Solved

Reverse within string

If input is a string 'yellow' the output should be 'leywol'. Locate the middle of the string and reverse the first (yel) and sec...

10 days ago

Solved

Minimum Distance Point to Segment

This Challenge is to determine the minimum distance from a 2-D line segment defined by two points to a point. The point is (p...

10 days ago

Solved

Property dispute!

Two neighbors have rectangular plots of land A and B. The surveyors give you the coordinates of each. If they overlap, there is ...

10 days ago

Solved

Project Euler: Problem 10, Sum of Primes

The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below the input, N. Thank you <http:/...

10 days ago

Solved

Extract diagonal of sparse quadratic form

Consider the matrix A and vector v given by, A=round(sprand(5e3,1e4,1/1e4*100)*100); v=randi(10,width(A),1); Write a rout...

10 days ago

Problem

Extract diagonal of sparse quadratic form

Consider the matrix A and vector v given by, A=round(sprand(5e3,1e4,1/1e4*100)*100); v=randi(10,width(A),1); Write a rout...

10 days ago | 1 | 4 solvers

Problem

2x2 binning of a large sparse matrix

Consider the 20000 x 20000 sparse matrix, A=round(sprand(2e4,2e4,1/1e4*100)*1000); The task is to divide this matrix into 2x...

11 days ago | 0 | 4 solvers

Solved

Do the line-segments intersect?

You are given two line segments. Do they cross? Consider one segment as (x1,y1) to (x2,y2), the other segment as (x3,y3) to (x4...

11 days ago

Solved

swap sign sum & multiply castles

It is an easy problem, if you know the answer. Given a square matrix of NxN ordinary numbers. Initially place N identical indi...

11 days ago

Solved

Flipping

Write code that can reverse the vector without using any sort of loop. Example Given the input vector A = [ 1 2 3 4 5...

11 days ago

Solved

Flip the diagonal values

Write a program that flip the elements of main diagonal , upper and lower diagonal values of a sqare matrix. For example if a ...

11 days ago

Solved

Flip the bit

Given an input character string (e.g. '1001'), return a character string with the bits flipped ('0110').

11 days ago

Solved

Flipping a Matrix

Flipping matrix up and down. If a central row is exists, leave it, and flip remaining rows. Example Mat = magic(3) ...

11 days ago