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James Tursa


3.033 total contributions since 2007

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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Answered
How to find the angle between two quaternions?
For example purposes I am using the coordinate frames as ECI and BODY Q1 = quaternion from ECI->BODY1 Q2 = quaternion from ECI...

1 dag ago | 1

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Answered
for loop, conditional operator
You are creating the variable filling_degree_regionI_new inside a condition if statement. If the condition is never met, the va...

1 dag ago | 0

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Answered
Get next or prior single precision value MATLAB function ?
The designers of IEEE floating point were brilliant. The next largest value (in magnitude) is always obtained by just adding 1 t...

6 dagen ago | 0

Answered
Arrays from c to matlab.
v is pointer-to-double, *v is double. Everywhere inside generation() that you use v it needs to be *v instead.

7 dagen ago | 0

Answered
Shuffling and Using a Set of Six 52-Card Decks
It is not entirely clear what you want. Maybe this instead of the loop? shuffledcard = decksofcards(randomcards);

9 dagen ago | 0

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How to add new elements in a big array
Maybe assign into elements of N with indexing: N(j) = length(group);

18 dagen ago | 1

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Answered
filling each row of a matrix using values from a vector
Assuming x starts as a 4x4 matrix (instead of a 3x4 matrix): x(sub2ind(size(x),(1:numel(u))',u)) = 1;

19 dagen ago | 0

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Answered
Convert double array into column vector
Maybe one of these? reshape(f,1,[]) f(:).'

19 dagen ago | 0

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uint16 to uint8
u16 = your uint16 variable u8 = typecast(u16,'uint8');

19 dagen ago | 0

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Answered
API changes in R2019a?
I don't know if this is the cause of your problems, but there was a change to the low level mxArray variable structure in R2019a...

19 dagen ago | 0

Answered
complex number inside cell array
This might be done better with a loop, but here is a method using cellfun c = your cell array containing complex numbers resul...

19 dagen ago | 0

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Answered
RK4 orbit problem
Couple of things: 1) You have picked the most convoluted method of coding your equations. Having four separate variables for yo...

19 dagen ago | 1

Answered
Portable declaration of REAL variables in mex gateway for Fortran
The REAL(kind(0.0D0)) vs REAL*8 discussion (and INTEGER*4 vs INTEGER etc) is a compiler issue, not a mex issue. As long as your...

20 dagen ago | 0

Answered
The return type of mxIsDouble, mxIsSingle, and mxIsClass (mex for Fortran)
Do what the documentation says and use INTEGER*4. Yes, it is non-standard but you are very unlikely to run into a compiler that...

20 dagen ago | 0

Answered
How can I generate random single precision (float32) numbers ?
For the generic answer with all bit patterns possible and selected with equal probability (including inf & nan & denorm) your "b...

23 dagen ago | 1

Answered
How can I show the 4-byte hex representation of a single precison float value?
s = your single float number h = dec2hex(typecast(s,'uint32'),8) And the reverse is s = typecast(uint32(hex2dec(h)),'single')...

25 dagen ago | 0

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Answered
Error using mex: undefined reference for user build package
Try looking in the MATLAB/R2019a/extern/lib folder for versions of these files appropriate for your system. They might have slig...

ongeveer een maand ago | 0

Answered
Problem with MexFunction and MexGetPr
Impossible to answer without seeing the code for the functionsum( ) function. Maybe you could post that? Maybe all you need to...

ongeveer een maand ago | 0

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Answered
Unexpected numerical error in built-in cross product
When I calculate things from scratch, everything works to the expected precision. E.g., run this code: % From post rTAN = [6.2...

ongeveer 2 maanden ago | 2

Answered
MEX crashes when called twice in succession (Same input)
Here is one cause of a crash: mwIndex *subs; subs[0]=1; subs[1]=1; You are dereferencing an uninitialized pointer on that se...

ongeveer 2 maanden ago | 0

Answered
Change sign of descending values
Is this what you want? x = your vector of values d = [1;diff(x)]; x(d<0) = -x(d<0);

ongeveer 2 maanden ago | 1

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Answered
Trouble with declaring function output
function data = importer

ongeveer 2 maanden ago | 1

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Answered
how to iterate a matrix for multiple times
E.g., here is a possible outline n = 30; % the number of iterations M = rand(5,5); % some initial matrix for k=1:n M = 2...

ongeveer 2 maanden ago | 1

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Answered
Using the dms2degree Command Sequentially to Populate an Array using a Sub-routine
With a for-loop, you need to use A in all of your indexing and use the [ ] brackets to form a vector input (and spell the functi...

ongeveer 2 maanden ago | 0

Answered
Write a function called valid_date that takes three positive integer scalar inputs year, month, day. If these three represent a valid date, return a logical true, otherwise false. The name of the output argument is valid.
Looks like you are taking the same class as Rahul. Rather than repeat my answer here, I will simply direct you to the link: ht...

ongeveer 2 maanden ago | 0

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Answered
sum of multiplication for a vector and matrix
result = sum(b*A);

ongeveer 2 maanden ago | 1

Answered
I need some help in seeing where I am going wrong and how to proceed with writing a particular funciton for a MATLAB course I am taking please.
Some issues: n is a fixed input ... you should not be changing n inside your function. Get rid of that n = n + 1 statement. T...

ongeveer 2 maanden ago | 1

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Answered
Use of int vs size_t in mex compilation of C-function dgemm.
If you are linking to the MATLAB supplied BLAS/LAPACK libraries, then all of the integer types being used for arguments to these...

ongeveer 2 maanden ago | 0

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Answered
For loop to extract every 3rd column out of matrix and assign as variable name
Do not do this! This will only lead to headaches downstream in your code for processing these variables (you will need to use m...

ongeveer 2 maanden ago | 1

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Answered
random generator on level of bytes
Generate random integers and then multiply them by 8 to guarantee that the result is divisible by 8. E.g., something like: max_...

ongeveer 2 maanden ago | 2

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