James Tursa

Last seen: Today | Active since 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 ...

7 hours ago | 0

Answered
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...

8 hours ago | 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...

8 hours ago | 0

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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...

7 days ago | 3 answers | 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...

9 days ago | 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...

11 days ago | 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...

1 month ago | 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...

1 month ago | 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...

2 months ago | 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 months ago | 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 months ago | 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 months ago | 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.*...

4 months ago | 2

Answered
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 months ago | 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 months ago | 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 months ago | 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 months ago | 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 months ago | 2 answers | 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 months ago | 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 months ago | 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 months ago | 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 months ago | 1

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Answered
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...

7 months ago | 1

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

7 months ago | 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 months ago | 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 months ago | 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 months ago | 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 months ago | 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 months ago | 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, ...

8 months ago | 0

James Tursa

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