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James Tursa


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3.601 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
I'm new to matlab and am trying to sort an array in ascending order without using the sort command. How would I rectify this?
This is a "bubble sort" and you have two problems. First, as mentioned by Walter, is your indexing max value is one too big. Y...

alrededor de 18 horas ago | 1

Answered
Preallocating a sparse matrix, then entering values column by column takes too much time. Is there a more efficient way ?
The problem is that every time you change the elements of Q, even if it is only one element change, MATLAB generally has to copy...

2 días ago | 0

Answered
How to optimize matrix multiplication speed?
This looks like a covariance matrix update to me. The matrix multiplies are already done by highly optimized multi-threaded com...

3 días ago | 0

Answered
How to limit calculation precision?
You can get about that precision (a little less) by using the half data type: https://www.mathworks.com/help/fixedpoint/ref/hal...

6 días ago | 1

Answered
FOR LOOP NOT WORKING
Index your answers. E.g., if EXANGLES(i) < 90 EVANGLE1(i) = EVSUB1-FT126; elseif EXANGLES(i) == 90 ...

7 días ago | 0

Answered
Numerical Solution of the System of four Coupled Nonlinear ODEs by Runge-Kutta Fourth Order Method
I will point out some problems, and then suggest a much easier way to do this. Start with your first couple of lines in the loo...

7 días ago | 0

Answered
can i get mex files in matlab format?
Mex files are compiled (i.e., machine language) DLL files. You cannot view them in MATLAB m-file format. If you have the C/C++...

7 días ago | 0

| accepted

Answered
I need help obtaining the values c1,c2.c3 from a least squares fit of the data.
It appears to me that your equation is linear in c1, c2, c3. Just make a matrix equation out of this and then apply your least ...

8 días ago | 0

Answered
How to add an NxN matrix with K pages ?
You are correct, sum(A,3) is the correct syntax to use. This sums across the 3rd dimension.

13 días ago | 0

Answered
How do I vectorize matrices of specific modes of a tensor?
Is this what you want? x = your 250 x 250 x 183 array result = reshape(x,250*250,183);

15 días ago | 0

Answered
Why the memory Limitation to a data structure in cpp: size of "XXX::C_SubNetwork::S_ListBuffer [3]" >= 256 Mb and can I raise the limit higher?
This looks like you are declaring this variable as a local variable, in which case the memory for it will come off of the stack....

16 días ago | 0

Answered
mxCreateNumericMatrix and sparse matrix in C/Matlab hybrid programming
Convert the index arrays to double either inside the C code or on the Engine side. E.g., engEvalString(ep, "MS=sparse(double(MI...

19 días ago | 0

Answered
Converting double values file to 2 byte per sample.
If you want a two byte floating point representation you can use half precision. E.g., https://www.mathworks.com/matlabcentral/...

21 días ago | 0

Answered
How can I multiply N dimensional matrices
Other options from the FEX: https://www.mathworks.com/matlabcentral/fileexchange/8773-multiple-matrix-multiplications-with-arra...

21 días ago | 1

Answered
whats difference beetween angvel and rotvec?
I don't have a version of MATLAB installed that has the angvel( ) and rotvec( ) functions, so I can only make an educated guess....

22 días ago | 0

Answered
Strncpy/Strncpy_s is supported by Matlab
Your code has bugs. That is why it is crashing. The bugs are caused by these lines: main(); // You call main without any ...

22 días ago | 0

Answered
Fast conversion of 2 matrices to 1 complex matrix
See this FEX submission for reading and writing interleaved complex data in R2018a or later without extra data copies: https://...

29 días ago | 0

Answered
How to replace leading zeroes by spaces with regexprep
One way: fun = @(x)sprintf(['%' num2str(numel(x)) 'd'],str2double(x)); d = cellfun(fun,a,'uni',false); e = cellfun(fun,b,'uni...

29 días ago | 0

Answered
trimming matrix arrays arranged within cell arrays
It is not clear whether you want the rows or columns trimmed. Maybe one of these is what you want? TrimmedArray = cellfun(@(x) ...

29 días ago | 0

Answered
Runge-Kutta 4th order function error (Matrix dimensions must agree)
Your RK_4 function is not set up to handle vector equations ... it is only set up to handle scalar equations. Also you are not ...

29 días ago | 0

Answered
How to pass arguments by reference from Matlab?
doc loadlibrary Create a C header file that gives prototypes for the Fortran subroutines and treat the Fortran arguments as poi...

alrededor de 1 mes ago | 0

Answered
how to create an array of all permutations
If you want all of them in an array (which might be too large if the number of digits is too large), you can use n = number of ...

alrededor de 1 mes ago | 0

| accepted

Answered
Trying to do calculations for density
Why do you have these lines in your function: P_t=4; P_s=3; H=25; Aren't these variable supposed to be input arguments? See...

alrededor de 1 mes ago | 0

| accepted

Submitted


freadcomplex and fwritecomplex
Mex routines that read and write interleaved complex data files for MATLAB R2018a or later without extra data copy.

alrededor de 1 mes ago | 3 downloads |

Answered
efficient ways to read and write complex valued data
A mex routine to accomplish this that doesn't use any hacks can be found here: https://www.mathworks.com/matlabcentral/fileexch...

alrededor de 1 mes ago | 0

| accepted

Answered
efficient ways to read and write complex valued data
This may not apply to you, but if you have R2018a or later you can just fread( ) into a real variable directly the interleaved d...

alrededor de 1 mes ago | 0

Answered
Changing contents of Cell Array mex files
When you mxDestroyArray a cell array or struct array, it does a deep destroy. Meaning all of the cell array or struct array ele...

alrededor de 1 mes ago | 0

| accepted

Answered
solution with the Runge-Kutta method HELPP
This is clearly a homework/exam question, so I will only offer hints. The code you have posted is for a single scalar different...

alrededor de 1 mes ago | 0

Answered
How could I use MATLAB to solve for x with this equation, 0=a*x^(3)+b*x^(-1)+c.
Just use the roots( ) function. If you have a negative integer power of x in the expression such as x^(-n), then multiply every...

alrededor de 1 mes ago | 0

Answered
reshape loop resulted cell array
result = cell2mat(c1(:))';

alrededor de 2 meses ago | 0

| accepted

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