James Tursa
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3,637 total contributions since 2007Interested 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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Awarded to James Tursa on 26 Feb 2012
Markov Chain probability steady state
Hint: The probability of moving from one state to another state in n steps is P^n
16 hours ago | 0
Factorial without the Command
You could use either use a loop to multiply all of the numbers from 1 to n, or use recursion to multiply n by the factorial of n...
1 day ago | 0
Inputs a Vector and Returns the Second Smallest Element
Your algorithm always replaces Smallest and SecondSmallest at each iteration. Does that make sense? E.g., if the current Smalle...
1 day ago | 0
Hex to float like python struct.unpack()
Could be a Big Endian vs Little Endian thing. E.g., inserting a swapbytes( ) step: >> hex = 'C956F53D' hex = 'C956F53D' ...
2 days ago | 0
Python to MATLAB accuracy
Probably not. The trailing bits of floating point calculations in general can't be trusted. It you change the order of the calc...
2 days ago | 0
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solving coefficient with linear algebra
You basically have this: [ONES_COLUMN, X_COLUMN, Y_COLUMN] * p = DATA You know all the CAPS stuff. So just use the standard l...
3 days ago | 0
Composite Functions with a function with two ranges
For example, take the first one: (g o f)(x) This is just g(f(x)) which is g(x^2) Assuming we are talking only about real in...
8 days ago | 0
im trying to create a while loop for random numbers and it says if its even or odd
Change this while times < 20 to this while Ecounter < 20 and change this Ecounter = 0+1; to this ...
9 days ago | 0
The Body Mass Index, or BMI
Just get rid of these lines: function BMI=findbmi(Weight,Height)
9 days ago | 1
From where is this exp in syms calculus?
The solution space has multiple values, not just one. The solver has parameterized the solution space for you. There are multi...
16 days ago | 0
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simulate a dice throw
doc randi E.g., for a single throw you could use randi(6)
17 days ago | 1
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Why do I get "Array indices must be positive integers or logical values" error when using?
k is 3.5 So y(k-1) is y(2.5) and y(k-2) is y(1.5). The indexes are not positive integers, hence the error. Maybe you meant ...
17 days ago | 0
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How to fill mxArray with mxGetComplexDoubles?
No, this would not be expected to work. In the first place, you need to use mxDOUBLE_CLASS to create the mxArray, not mxSINGLE_...
18 days ago | 0
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The spacecraft free-fall math model
See this link for an example of the parachute problem: https://www.mathworks.com/matlabcentral/answers/516385-code-not-working-...
18 days ago | 0
Satellite Orbit, Friction Acceleration Function
See this link for an example that uses atmospheric drag with a satellite (in this case a satellite falling to Earth): https://w...
18 days ago | 0
Fibonacci Series Using Recursive Function
All of your recursive calls decrement n-1. Eventually you will wind up with the input n=0 and just return v=0, which is not wha...
18 days ago | 0
How to fix error: "Index in position 1 is invalid. Array indices must be positive integers or logical values"
Type the following at the command line: dbstop if error Then run your code. When the error occurs, the code will pause with a...
21 days ago | 0
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Why do I get this error message "Array indices must be positive integers or logical values."
You forgot to multiply between the y and (y-1) Z = x(:).^2.*y.*(y-1).*(y+1); Also, make sure to use element-wise operators (wi...
22 days ago | 0
pointers in object-oriented matlab programing
MATLAB does not have variable pointers ... at least not in the sense of C/C++ like you are probably alluding to.
23 days ago | 0
Recursion in matrix calculation
This uses recursive calls (CalDet calls CalDet with smaller matrices until the size is 1x1). I.e., the recursion continues all ...
24 days ago | 1
How C++ gets struct values from Matlab
Looks like your strings are char type and not the newer string type. So you can try the following: mxArray *mx; char *name; ...
24 days ago | 0
Checking whether two complex matrices are equal
You can't rely on floating point calculations to give exact results. See this link: https://ch.mathworks.com/matlabcentral/ans...
25 days ago | 2
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IMU orientation using AHRS filter
I haven't used either of those functions, but from reading the doc maybe you need to use the conjugate of the quaternions in you...
26 days ago | 1
Quick way to Invert the matrix (A+D) where the inverse of matrix A is known and the matrix D is diagonal.
Are the values in D small compared to A^-1 ? Maybe you can make use of one of the forms listed here: https://en.wikipedia.org/...
28 days ago | 0
How do I program the orbit of a particle that is experiencing Gravity & Radiation Force Pressure?
The differential equation is simply Newton's F = ma, where m is the mass of the object (M1) and a is the acceleration of the obj...
28 days ago | 0
Numerical integration RK4 for the given data
E.g., a VERY SIMPLISTIC approach showing one step of Euler integration dt = some delta time value q = [1,0,0,0]; % Initial qua...
1 month ago | 0
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How to convert this 2D code segment with random number into the FORTRAN code?
For your particular case, looks like the MATLAB code could reduce to: Nx = 4; Ny = 4; c1 = 0.12; rr = 0.0001; D = c1 + rr*(...
1 month ago | 1
Matrix multiply result different from loops
MATLAB calls 3rd party BLAS library code to do matrix multiply. This is a highly optimized multi-threaded library. The orderin...
1 month ago | 1
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Why does defining a system of ODEs a different, but similar way yield very different solutions?
Do you simply need to apply that factor in the 6th spot? (kred(t)*CNiIIIH - kox(t)*CNiIIH - k2*CNiIIH*CH)*(96485.33289/1e9);
1 month ago | 0
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