# James Tursa

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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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**Feeds**

Having issues writing matrix to a binary file.

@Rikin You forgot to read in the sizes. You only read in the double data. The two int32 variables at the front obviously were pa...

4 dagen ago | 1

an ode with arguements

Create a new function handle with your extra stuff. E.g., mufunT = @(eta,f) mufun(eta,f,guessT) [eta, f] = ode45(mufunT, [lins...

14 dagen ago | 0

Column to matix In matlab

Depends on how your data is currently stored. Suppose the data is currently in a vector v. Then matrix = reshape(v,50,10).'

15 dagen ago | 0

How do I process a string class in a mex function?

Strings are opaque objects (like classdef) and there are no API functions to get pointer access to the data areas. I am unaware...

15 dagen ago | 0

How to convert dates into Julian dates?

Based on your comment that you are expecting numbers in the range of 273,287,298, etc., if what you are after is actually "day ...

15 dagen ago | 0

How to create for loop for calculating euclidean distance of a matrix?

Does pdist() do what you want: https://www.mathworks.com/help/stats/pdist.html?s_tid=doc_ta

20 dagen ago | 0

converting 3d matrix into a cell array

x = rand(1001,259,259); result = arrayfun(@(k)squeeze(x(k,:,:)),1:size(x,1),'uni',false); size(result) size(result{1}) But, ...

ongeveer een maand ago | 0

How to implement the Central Difference method integrator for a two body problem?

You have: altitude tangential velocity If you just want the orbital period, you can calculate as follows using the Vis-Viva e...

ongeveer een maand ago | 0

Can multiple versions of MATLAB be installed on the same Windows PC using the same license number for code compatibility?"

Multiple MATLAB versions can be installed on the same machine as long as your license permits it. Both can even be run simultan...

ongeveer een maand ago | 0

How to calculate the angle between two 3D vectors?

See a discussion here (includes a tiny angle example): https://www.mathworks.com/matlabcentral/answers/101590-how-can-i-determi...

ongeveer een maand ago | 1

Double precision: Why does fprintf print "extra" wrong non zero digits?

The "extra" digits that look incorrect to you are simply the result of doing an exact conversion of the actual floating point bi...

ongeveer een maand ago | 1

| accepted

What does MATLAB actually do when switching precisions?

When converting from IEEE single to double, the sign bit is retained, the exponent bits are adjusted to match the same exponent ...

ongeveer een maand ago | 2

I want to solve ODE for a complex systems in a rk4 method

Just turn all the y( ) stuff into row or column vectors. E.g., suppose we use column vectors, then something like this ... y = ...

ongeveer 2 maanden ago | 0

| accepted

quat2angle / atan2 strange quadrant change when calculating angle

You don't show us your code, but in general I would note that angle changes like this are sometimes the result of whole quaterni...

ongeveer 2 maanden ago | 0

Active rotation with quaternions: from initial orientation given with Euler angles get the new orientation after an active rotation described by the qr quaternion.

Yes, for your convention q' = q * qr is mathematically correct. But note that this formula only works for certain quaternion co...

ongeveer 2 maanden ago | 1

| accepted

Question

Conjugate of Symbolic Root doesn't change anything

Reference question first asked here: https://stackoverflow.com/questions/78010011/matlab-bug-with-root-and-conj Basically, the...

2 maanden ago | 1 answer | 1

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answersparse matrix entries are not displayed correctly

I finally finished my sparse matrix integrity checker. You can find it in the FEX under the name SAREK (I think you will be able...

3 maanden ago | 0

the tranpose of transpose doed not equals the original matrix

I finally finished my sparse matrix integrity checker. You can find it in the FEX under the name SAREK (I think you will be able...

3 maanden ago | 2

Submitted

SAREK - Sparse Analyzer Real Et Komplex

The SAREK function analyzes a sparse matrix for integrity. Useful especially for checking sparse matrices built by 3rd party s/w...

3 maanden ago | 5 downloads |

Help with state representation of my 3-mass 2-spring system

The k terms in the equations above appear to be non-linear. Your A matrix doesn't account for the cubic parts.

3 maanden ago | 0

Calculate angles correctly between two vectors using the dot product.

Also see this related link for a robust method using atan2 that can recover small angles: https://www.mathworks.com/matlabcentr...

4 maanden ago | 0

How can I make memory persistent between calls to a MEX-file in MATLAB?

So, the accepted answer has bugs. Namely: They don't include the header for memcpy They don't check the input argument properl...

4 maanden ago | 0

Index in position 1 exceeds array bounds (must not exceed 8).

Here is how to debug these types of errors: Type the following at the command prompt: dbstop if error Then run your code. Whe...

4 maanden ago | 0

matlab mex in-place editing via "mxUnshareArray" or similar functionality

So, MATLAB has never officially supported modifying input variables in-place in a mex routine. There are potential side effects ...

4 maanden ago | 0

Static methods are unnecessary, right?

I use Constant Properties and Static Methods all the time in classes I am creating. In particular, when I am developing a group...

5 maanden ago | 1

Speed of the abs function

Although I applaud your thinking about this problem, this level of optimization is hard to achieve with a language such as MATLA...

5 maanden ago | 2

| accepted

How would I write these in MATLAB

Depends on what those subscripts mean. E.g., maybe this y41 = -(x41^1.5 * cos(x41)^3) + 40; y42 = x42 * sin(x42^2); or this ...

5 maanden ago | 0

| accepted

How to find roots of a quartic function with unknown constant coefficients?

You can look here: https://en.wikipedia.org/wiki/Quartic_function But the nature of the roots is going to depend on the value ...

5 maanden ago | 0

What calendar system does MATLAB use?

I know this is an old post, but the accepted answer is a bit misleading. MATLAB certainly does use a specific calendar system. ...

5 maanden ago | 3