James Tursa

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3,952 total contributions since 2007

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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Answered
Dealing with very small or very large numbers
I guess the obvious suggestion is to work in units of nanometers or maybe picometers instead of meters. Can you do that?

5 hours ago | 0

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How to use if statement in function?
Add this code to the top of your function: if( N <= 0 ) error('N needs to be > 0') end That being said, your loop probab...

1 day ago | 1

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How to build a quaternion from a normal vector?
If you have the Aerospace Toolbox, you could do the following n = 1x3 unit normal vector a = angle to rotate in radians v = 1...

1 day ago | 0

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Runge-Kutta 2
Normally one would plot the position, not the velocity. So I would have expected you to plot the "1" index of your solutions. ...

1 day ago | 0

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Double Variable Second order Differential Equation
Just write a derivative function using four states instead of two. The states will be x, y, dxdt, and dydt. The derivitives of...

1 day ago | 0

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How can I divide each element of a vector by each of the elements of another vector in MATLAB?
Assuming a and b are both column vectors, you can use automatic array expansion by transposing one of them and using element-wis...

2 days ago | 0

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"Array indicies must be positive integers" error
You can't have 0 or fractional indexing in MATLAB. Take this section of code for example: for t = 0:1:200 U(0,t) = ui; ...

2 days ago | 0

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what is the difference between the 2 codes ?
zeros([2,2]) passes one argument, a 2-element vector [2,2]. zeros(2,2) passes two arguments, the scalars 2 and 2. The result i...

2 days ago | 0

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Getting all Permutations of a 18+ integer vector
The number of different permutations of a vector of size n is n! (n factorial). So what you are attempting has these many possi...

3 days ago | 0

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Calculating a matrix with a specific form
You could rearrange the equations, isolate m(1), m(2), and m(3) and solve for them directly. E.g., rearrange the equations to f...

3 days ago | 2

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Combine logical arrays into one array
L = L1 | L2 | L3 | L4;

3 days ago | 0

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Answered
How to vectorise code involving matrix multiplications with vectors
See this link: https://www.mathworks.com/matlabcentral/answers/776812-how-to-vectorize-a-b-operation-on-slices-of-3d-matrices?s...

3 days ago | 0

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Answered
What is the corect code for writing an error message when a user inputs an array instead of a scalar value?
Several ways to test for a scalar. E.g., if( ~isscalar(x) ) error('Input is not a scalar'); end or if( numel(x) ~= 1 )...

3 days ago | 0

Answered
Calculating and and recording a vector during each iteration of a "while" loop.
E.g., using a counter to store all of your iteration data in a cell array and then post process this: k = 1; % the counter Rce...

3 days ago | 0

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Answered
Trying to separate Quaternion coefficients into array.
Use the double( ) function to convert to numeric array, then use regular indexing. E.g., try this function g = actfun(q) ...

3 days ago | 1

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quat2eul is giving me a strange result
Maybe all you have to do is add 2*pi to all results that are less than -pi to get things how you want.

8 days ago | 0

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Answered
Handling Inputs mex function
The prhs[ ] variables are of type pointer to mxArray ... you cannot use simple native C conversions with them. You must use som...

10 days ago | 0

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Answered
How can I fix this error?
Delete the extra closing parentheses. I.e., delete the paren where the red underline is.

11 days ago | 0

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Undefined function or variable t
Put this code in a separate file called Math.m % file Math.m function dxdt=Math(t,x1) % function name x=x1(1) y=x1(2) z=x1(...

11 days ago | 0

Answered
Generating a 4th order Runge-Kutta Integrator solver for the motion equation.
ode45( ) is not well suited to the orbit problem since the integration errors can systematically build up over time. You can tr...

11 days ago | 0

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ODE45 function for 3 Variables
This y0 = [0;0;0;0]; and this zF = 0; means that your derivative function will evaluate to 0 exactly, so the solution is 0 e...

11 days ago | 0

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Can anyone help?
Hint: Look at the results of this operation, and I think you can figure it out from there: x = [2;3;4]; % column vector y = 0:...

24 days ago | 0

Answered
How binary Random number generation upto n nodes ?
Here is how to get your stated desired output, but this is not random at all: r = dec2bin(0:(2^L-1)) - '0';

26 days ago | 0

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Answered
Undefined function or variable 'bisection'.
From the error message, it looks like you are calling the function using the name "bisection", but the actual name of the functi...

26 days ago | 0

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ODE45 in 3 dimensions with 6 initial conditions
I find it easier to keep the position elements together, and the velocity elements together, in the state vector. So I would de...

26 days ago | 1

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Answered
Generate a Runge-Kutta Integrator solver for the orbital motion equation, when given the initial conditions. Execute for 500 seconds.
First, I find it easier to keep the position elements together, and the velocity elements together, in the state vector. So I w...

27 days ago | 1

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Answered
Runge-Kutta method, cannot produce the correct graphs
You need to index x in your calculations. E.g., q1 = f(x(i),y(i)); q2 = f(x(i)+h, y(i)+h*q1); You should init...

1 month ago | 0

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Answered
Working with an equation and variables from user.
You can construct a function handle as follows: f = str2func(['@(x,y)' str1]); You can then use this function handle to evalua...

1 month ago | 0

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Answered
A matlab code that allows the user to put inputs as
See the input( ) function for getting input from the user: https://www.mathworks.com/help/matlab/ref/input.html?searchHighlight...

1 month ago | 0

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Using a for loop determine how many months it would take to acquire £500,000.
You don't know the number of iterations it will take, so that is your clue that a for-loop is not appropriate. Use a while-loop...

1 month ago | 0