James Tursa

Last seen: Today | Actif depuis 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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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 ...

11 jours il y a | 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...

11 jours il y a | 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...

11 jours il y a | 0

Question

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...

18 jours il y a | 3 réponses | 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...

19 jours il y a | 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...

22 jours il y a | 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...

environ un mois il y a | 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...

environ un mois il y a | 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...

environ 2 mois il y a | 0

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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...

2 mois il y a | 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:...

2 mois il y a | 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...

3 mois il y a | 33

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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.*...

5 mois il y a | 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...

5 mois il y a | 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?

6 mois il y a | 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...

6 mois il y a | 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 ...

6 mois il y a | 0

Question

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...

7 mois il y a | 2 réponses | 0

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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...

7 mois il y a | 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...

7 mois il y a | 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...

7 mois il y a | 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...

7 mois il y a | 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...

8 mois il y a | 1

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How to write a matrix with elements 10,30,10
Use brackets M2 = [10,30,10]

8 mois il y a | 0

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an ode with arguements
Create a new function handle with your extra stuff. E.g., mufunT = @(eta,f) mufun(eta,f,guessT) [eta, f] = ode45(mufunT, [lins...

8 mois il y a | 0

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Column to matix In matlab
Depends on how your data is currently stored. Suppose the data is currently in a vector v. Then matrix = reshape(v,50,10).'

8 mois il y a | 0

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How do I process a string class in a mex function?
Strings are opaque objects (like classdef) and there are no API functions to get pointer access to the data areas. I am unaware...

8 mois il y a | 0

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How to convert dates into Julian dates?
Based on your comment that you are expecting numbers in the range of 273,287,298, etc., if what you are after is actually "day ...

8 mois il y a | 0

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How to create for loop for calculating euclidean distance of a matrix?
Does pdist() do what you want: https://www.mathworks.com/help/stats/pdist.html?s_tid=doc_ta

8 mois il y a | 0

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converting 3d matrix into a cell array
x = rand(1001,259,259); result = arrayfun(@(k)squeeze(x(k,:,:)),1:size(x,1),'uni',false); size(result) size(result{1}) But, ...

9 mois il y a | 0

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James Tursa

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