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James Tursa


3.039 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
Pass pointer to scalar variable in mex function
"... The only way I've gotten around this before is by making the scalar variable into a vector and just using the first element...

1 giorno ago | 0

Answered
2D summation loop
Take the denominator for instance. Literally written out, this would be denominator = 0; for k=1:K denominator = denomin...

2 giorni ago | 0

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Answered
Get a matrix by interaction
Maybe use cell arrays. E.g., BCG{gen} = horzcat (dx1, dy1, dx2, dy2, dx3, dy3, SLL); Then everywhere downstream in your code, ...

3 giorni ago | 0

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Answered
Implicit expansion with empty arrays
In the 1st case, you are expanding a dimension of 1 (the 3rd dimension of the first operand) to 0, so it is scalar expansion. I...

4 giorni ago | 0

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Answered
how to add all 2d matrices in a 4D matrix???
sum(sum(your_matrix,4),3) or sum(reshape(your_matrix,10,50,[]),3)

4 giorni ago | 0

Answered
Save values in each iteration
The loops aren't needed. E.g., Ccl = 21; % Number of column elements gene = 5; % Number of times the column is generated min...

4 giorni ago | 0

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...

8 giorni 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...

8 giorni 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...

12 giorni ago | 0

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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.

14 giorni 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);

15 giorni ago | 0

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

24 giorni 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;

25 giorni ago | 0

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

25 giorni ago | 0

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

26 giorni 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...

26 giorni 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...

26 giorni 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...

26 giorni 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...

27 giorni 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...

27 giorni 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...

29 giorni 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')...

circa un mese 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...

circa un mese 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...

circa un mese 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...

circa 2 mesi 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...

circa 2 mesi 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);

circa 2 mesi ago | 1

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Answered
Trouble with declaring function output
function data = importer

circa 2 mesi 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...

circa 2 mesi 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...

circa 2 mesi ago | 0

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