James Tursa

Last seen: Today | Con actividad desde 2007

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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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Matlab crashed when running Pardiso mex file with certain input size
I haven't had time to look at this thoroughly, and I am unfamiliar with PARDISO, but the symptoms you describe are usually the c...

12 días hace | 0

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Setting the Output of a MEX Function as One of the Inputs After In Place Manipulation
A couple of problems. 1) First, your crash is caused by this: mxSetDoubles(plhs[0], mxGetDoubles(prhs[1])); You cannot atta...

17 días hace | 1

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Pregunta

Why is vpa not converting double accurately?
I ran across this example that I don't understand. I don't use the Symbolic Toolbox much, but I thought vpa by default converte...

alrededor de 1 mes hace | 1 respuesta | 3

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Matlab crashes when Intel MKL's function Pardiso is called
Just seeing this post. Too late for OP, but for future readers here are my comments: ---------------------------------------- ...

alrededor de 1 mes hace | 0

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Plots saved as JPEG look awful. How to improve?
You might also explore export_fig from Yair Altman, found here: https://www.mathworks.com/matlabcentral/fileexchange/23629-expo...

alrededor de 1 mes hace | 0

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need to vectorize efficiently calculating only certain values in the matrix multiplication A * B, using a logical array L the size of A * B
You can try this naive mex routine. Not optimized at all for cache hits or patterns in L. Might be faster to transpose A first, ...

2 meses hace | 1

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ode45 code for 2 body problem
Your system has an initial non-zero total linear momentum. Recall that the 2-Body Problem has a constant center of mass motion ...

2 meses hace | 0

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Get total number of leap seconds relative to gps time
To convert a GPS timestamp to a UTC time, use the UTCLeapSeconds time zone which automatically accounts for leap seconds in the ...

5 meses hace | 0

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How to use datetime with leap second strings?
@Peter Perkins Thanks for the reply. My comments ... "... I'd be curious to hear where you are getting timestamps that honor l...

5 meses hace | 0

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How to preserve nanosecond precision in datetime calculations (for large numbers)
This question already has an accepted answer, but I would like to add my observations on this topic. datetime: Internally hold...

5 meses hace | 0

Pregunta

How to use datetime with leap second strings?
Suppose we have the following date time string: ds1 = "30-Jun-1972 23:59:59.5"; You can convert that to a datetime easily: da...

5 meses hace | 3 respuestas | 0

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Why Is Colon Operator Not Equivalent To linspace Command?
The short answer is that the algorithms are different. In the first place, 0.08 cannot be represented exactly in IEEE double pre...

5 meses hace | 3

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C++ Mex function being passed a MATLAB class object
mxDuplicateArray( ) does indeed create deep copies ... or at least it used to. Not sure why that would have changed. There migh...

5 meses hace | 1

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Error using mex, building with 'MinGW64 Compiler (FORTRAN)'
FYI, you should never use literal constants in a Fortran API call, because you can't be sure whether the literal integer(4) or i...

6 meses hace | 1

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How to pass a Matlab function handle to C-Mex Code
To use a function handle in a mex function with C array as an input to the function handle, you can use mexCallMATLAB( ) with th...

6 meses hace | 2

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Kalman Filter Velocity data looking too similar to position data
Your velocity vf and position rf calculations as shown represent "change" over dt, not current value. Think about it. If you had...

7 meses hace | 0

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Respondida
Is giving a space after comma in functions the convention?
A MATLAB specific thing that is somewhat related is that spacing is important in concatenation. E.g., the following look similar...

7 meses hace | 1

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My Numerical Solution doesn't align with the exact solution
Assuming your state is [vc,vc'] in that order, then it appears your initial conditions are backwards and should be this instead:...

7 meses hace | 1

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How can I find index of element in array?
To find the index of a specific integer value (without roundoff error) in an array of integers, use the "find" function and == o...

8 meses hace | 33

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Respondida
Order terms in symbolic poly converted to string
Brute force if you need the string for some reason? syms x ex = taylor(exp(x),order=3) [C,T] = coeffs(ex) terms = fliplr(C.*...

9 meses hace | 2

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How can we convert a datetime into a string that represents a Unix timestamp in nanoseconds?
Another workaround that avoids the lossy duration type issues and doesn't need the messy struct solution for this particular cas...

10 meses hace | 0

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Write a function called freezing that takes a vector of numbers that correspond to daily low temperatures in Fahrenheit. Return numfreeze, the number of days with sub freezing
Hint: Is it freezing when the temperature is above 32 or below 32? And what have you coded?

11 meses hace | 2

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How to do differentiation in Matlab
Are you just asking for piecewise linear differencing for derivative calculations between the points? E.g., THT = 0:12:360; L...

11 meses hace | 0

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Matlab got this wrong: Limit as n goes to infinity: (1+(i/n))^(n^2). Matlab says it's exp(2), which is wrong. Pls confirm.
I have been looking at this for a couple of days now and have finally convinced myself that this limit doesn't exist and MATLAB ...

11 meses hace | 0

Pregunta

Duration type doesn't preserve seconds accuracy
I've been working on some time conversion routines and ran into an issue I didn't expect. Basically, the duration type doesn't p...

12 meses hace | 2 respuestas | 0

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Respondida
Rank value matrix from 3d Matrix
Might be easier to permute first so that your 2D matrices are in the first two spots. Then simply use sort() to get the rank ind...

12 meses hace | 0

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Error with matrix calculation
We don't have all the variables necessary to run your code, but guessing that maybe you need element-wise divide instead of matr...

12 meses hace | 1

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Unable to resolve the name 'half.typecast'
half is an opaque data type in MATLAB, not a regular numeric type like double and single. I tried to get TMW to change this to a...

12 meses hace | 1

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What does it mean "/Multiple" after variable name in *.mat file?
If the file is written by a 3rd party tool, it is probably written in uncompressed format. In that case, and if the /Multiple is...

12 meses hace | 1

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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...

alrededor de 1 año hace | 1

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