# James Tursa

Interested in external applications, mex & engine applications with Fortran, C, C++, etc, particularly in the areas of speed improvement and memory management efficiencies.

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**Content Feed**

help with parallelization of matrix operations

Both of these operations can be multi-threaded in the background, but this kind of timing test is not straightforward to do beca...

ongeveer 4 uur ago | 0

Field II kidney example does not work due to "Requested array exceeds the maximum possible variable size." error

At first glance this is the obvious problem in the original source code: The dimensions array needs to be the proper integer si...

2 dagen ago | 0

Question

Is there a classdef startup/initializer method?

When a classdef is first loaded into memory (via object instance creation or static method call etc.), is there a way to get a s...

3 dagen ago | 1 answer | 1

### 1

answerQuestion

How to update leap seconds

The current version of MATLAB has a function to give you the leap second information that it is using. E.g., [T,vers] = leapsec...

7 dagen ago | 2 answers | 0

### 2

answersA MEX solution to split classdef-defined object arrays into cells

You need to use mxGetProperty( ) to get at the properties of a classdef object. And since this returns a deep copy, no need for ...

10 dagen ago | 1

| accepted

Why does accessing a multi-dimensional array with fewer indices than its total dimensions not result in an error in MATLAB R2022b?

The accepted answer is misleading. When you access a multi-dimensional array with fewer indexes than its total dimensions, MATLA...

21 dagen ago | 3

Create Mex files for Matlab, from .FOR files of Fortran

So, I haven't had access to a Fortran compiler in over 10 years. And as a result I haven't been maintaining any of my Fortran F...

ongeveer een maand ago | 0

Unusal error "Current use of the variable is inconsistent with its previous use or definition".

See how the +b is purple? That means MATLAB thinks you are invoking a as a function with +b as a character string input. Hence ...

ongeveer een maand ago | 1

| accepted

Question

Incorrect datetime UTCLeapSeconds conversion

I am working with leap second data, and as part of the calculations I did this for a particular leap second: dt1 = datetime(197...

ongeveer 2 maanden ago | 1 answer | 0

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answerHow to add rows containing zeros to a matrix

E.g., one way using the end syntax: my_matrix = reshape(1:12,3,4) n = 4; % number of rows to append my_matrix(end+n,1) = 0 B...

ongeveer 2 maanden ago | 0

error using tranpose (recieving permute error )

If you are trying to transpose the initial 2D pages of your variable, you can do this: pagetranspose(featvales) Or this: d = ...

ongeveer 2 maanden ago | 0

Error L2 is not defined

You have a fundamental problem with your code. You have a 2nd order ODE, which means there will be two states you need to carry ...

ongeveer 2 maanden ago | 0

Use Indexing for more than 1 dimension of array simultaneously

Yet another way using linear indexing (showing what sub2ind( ) does internally): matrix = rand(10, 3); idx = [1; 2; 2; 3; 1; 2...

ongeveer 2 maanden ago | 0

Indexing and turning into column vector

Not really. It's going to be a two-step process no matter how you do it (without resorting to a mex routine, which isn't worth i...

2 maanden ago | 0

| accepted

how to make a single array out of 2 arrays

Just use indexing. E.g., odd=[0.4357, 0.78208,0.6245] even=[0.48004,1.29188,1.54668,0.82376] both(1:2:5) = odd both(2:2:8) =...

2 maanden ago | 0

| accepted

Difference between 2 orientations

I would do your method #3 involving quaternions. This would give you the "smallest" rotation between the two attitudes. But you ...

2 maanden ago | 1

Implicit casting overhead from real to complex when multiplying two matrices

This is not a natively supported operation (to use your terms). Yes, the real matrix must be first upconverted to a complex matr...

2 maanden ago | 1

why do we initialize any vector or matrices with zero.

If you know you will be filling in the variable elements downstream anyway, it would be faster to just allocate the memory and n...

3 maanden ago | 0

Complex matrix multiplication with pagemtimes

This really has nothing to do with the maturity of MATLAB ... every language that uses BLAS routines in the background will have...

3 maanden ago | 2

| accepted

Matrix power vs for loop

Note that the A^endtime method is probably going to be more accurate as endtime gets larger. The loop method can have a tendancy...

3 maanden ago | 0

error: matrix dimensions must agree

I would presume you may need element-wise operators. Try this: func = @(K_a,freq)(-K_a./(tan(2*pi*freq*h.*(1 + 0.19./((K_a/60 +...

3 maanden ago | 0

Average every 3 rows of 1 column in a 12 x 8 array

E.g., Data = [ 34 6 4 -6.60874766440390 -40.7725049965035 16217 0.289000000000000 1.02200000000000 35 6 5 -6.54326464...

3 maanden ago | 0

| accepted

Converting 2D cell array to 3D matrix

E.g., MyCell = repmat({(1:4)'},2,3) % small sample data [m,n] = size(MyCell); reshape(cell2mat(MyCell(:)').',m,n,[]) size(an...

4 maanden ago | 1

| accepted

How can I calculate the "Median" of floating point numbers

E.g., x = randi(10,2,3) y = randi(10,2,3) z = randi(10,2,3) xyz = cat(3,x,y,z) result = median(xyz,3)

4 maanden ago | 0

| accepted

transposing 3d matrix with permute function

MATLAB does not store trailing singleton (1) dimensions beyond the 2nd dimension. Once you permute that 1 into the 3rd dimension...

4 maanden ago | 2

Question

LU decomposition algorithm change

For this particular example: A=[ 1 2 3; 4 5 6; 7 8 9; 10 11 12]; I get two different results depending on...

4 maanden ago | 2 answers | 0

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answersInserting a double to a cell

E.g., x = randi(100,10,10) % sample data columns = [4,7]; % columns to check minx = min(x(:,columns)) % minimum of the two co...

4 maanden ago | 0

| accepted

Using Matlab to solve 1D Schrödinger Equation (Strange Eigenfunctions)

Python: return is misspelled retrun The mL2V( ) function returns 1000*(y-1/2)**2 I don't see where y is defined prior to the ...

4 maanden ago | 0

1×0 empty double row vector using find

Welcome to the world of floating point arithmetic. For your specific example, they are not equal. E.g., x=[0 0.1 0.2 0.3 0.4 0....

4 maanden ago | 1