Community Profile # James Tursa

Last seen: Today 2007년부터 활동

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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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 ...

2일 전 | 0

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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. ...

13일 전 | 3

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Rungekuttan for a system of 2 DOE functions
It would be better to have a single state vector for your solution so that you can easily compare your results to MATLAB ode45( ...

17일 전 | 0

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How much data does an array take?
The data is held in contiguous memory, so yes for a full real double an NxN matrix would take 8*N^2 bytes for the data. Then the...

26일 전 | 0

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Multiply matrices in cell array by another matrix
You may be stuck with the loop. There are ways to rearrange and stack things so that you can do everything in a single matrix m...

대략 1개월 전 | 0

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Try data = fread(fd, '*int16'); When you use 'int16' for the type to read, MATLAB reads as int16 and then converts to double (...

대략 1개월 전 | 1

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Incorrect Dimensions for matrix multiplication
Because you are using matrix operators instead of element-wise operators. Try this: Rtf=(cosh(m.*Lf)+(h./(m.*Kf)).*sinh(m.*Lf))...

대략 2개월 전 | 0

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Why is pow2() slow? Fastest way?
Another way is just to add d to the exponent bits. Probably fastest to do this in a mex routine where edge checking can easily b...

대략 2개월 전 | 0

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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];...

2개월 전 | 2

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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...

2개월 전 | 0

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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...

2개월 전 | 0

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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...

2개월 전 | 답변 수: 1 | 1

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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...

3개월 전 | 답변 수: 2 | 0

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A 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 ...

3개월 전 | 1

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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...

3개월 전 | 3

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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...

4개월 전 | 0

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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 ...

4개월 전 | 1

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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...

4개월 전 | 답변 수: 1 | 0

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How 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...

4개월 전 | 0

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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 = ...

4개월 전 | 0

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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 ...

4개월 전 | 0

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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...

4개월 전 | 0

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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...

4개월 전 | 0

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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) =...

4개월 전 | 0

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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 ...

5개월 전 | 1

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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...

5개월 전 | 1

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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...

5개월 전 | 0

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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...

5개월 전 | 2

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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...

5개월 전 | 0

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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 +...

5개월 전 | 0