# 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**

Values are getting converted to double automatically.

Here is what I get just displaying the character string. I inserted brackets [ ] for concatenation: ab=[0.5,0.75,1,1.25,1.5,2];...

2 dagar ago | 2

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...

8 dagar 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...

10 dagar 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...

11 dagar 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...

15 dagar 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 ...

18 dagar 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...

29 dagar 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...

ungefär 2 månader 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 ...

ungefär 2 månader 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...

ungefär 2 månader 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...

2 månader 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 = ...

2 månader 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 ...

2 månader 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...

2 månader 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 månader 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 månader 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 ...

3 månader 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...

3 månader 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 månader 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 månader 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 månader 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 månader 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 månader 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 månader 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 månader 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 månader 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 månader ago | 2 answers | 0

### 2

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 månader 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 månader ago | 0