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James Tursa


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3,735 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
How to create a periodic function?
Not sure what you mean by "repeated at [2,10]". Maybe this: y = mod(x,2); ix = y > 1; y(ix) = 2 - y(ix);

6 hours ago | 0

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Answered
How do i use output of one function as input to the other ?
You can do this at the point where you are calling the function neg. E.g., z = neg(pos(x,y),q);

12 hours ago | 0

Answered
Index in position 1 is invalid. Array indices must be positive integers or logical values.
When i=m in your loop you try to access kernel(m-m,n-j) which is kernel(0,m-j), and 0 is an invalid index. Similar problems wit...

12 hours ago | 0

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Answered
Solve a differential equation system with 4th order Runge-Kutta method with three equations
Not sure if you actually use t in your derivative functions, but you are missing that input from your j1, k1, and l1 code: ...

15 hours ago | 0

Answered
sum of cubes question
This homework question is poorly written: It seems like the intent of the n is to use it as the upper limit of the for-loop, bu...

16 hours ago | 1

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Answered
Calling a function from another function
my_first_function1( ) doesn't return any value to the caller. To return a value you use this syntax: function absx = my_first_...

1 day ago | 1

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Answered
Numerical integration of the differential equation of motion of the two body problem
Your biggest problem is that you don't carry enough states in your derivative function. Your ODE is a 3D 2nd order equation, so...

1 day ago | 0

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Answered
How to swap multiple rows of a matrix at a time
A = your matrix A([1:63,142:202],:) = A([142:202,1:63],:);

2 days ago | 0

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Answered
Probability of binary sequence with Monte Carlo
First point is that probability of stopping at n=3 is not 2/6, it is (3/4)*(2/6) because you have to include the probablility th...

5 days ago | 1

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Answered
Problem at +/- 180 degrees in orientation estimation from IMU data
You can try the unwrap( ) function: https://www.mathworks.com/help/matlab/ref/unwrap.html

5 days ago | 0

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Answered
Help with secant method
You might look here which even includes example code: https://en.wikipedia.org/wiki/Secant_method

5 days ago | 0

Answered
How do I add an integer to every or any nth row
A(k,:) is the k'th row of A A(:,k) is the k'th column of A A([k m p],:) is the sub-matrix formed from the k'th, m'th, and p'th...

6 days ago | 1

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Answered
First and last occurrence of an element in an array
So the description of the problem doesn't say anything about consecutive values, so the code you have for that should be elimina...

6 days ago | 0

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Answered
Parse error at ']'
Looks like you just need commas instead of periods. E.g., [r,i,v,dr,di,dv]

6 days ago | 0

Answered
Simple Blackjack Simulation in MATLAB
A few things ... Seems like you should have this: deck = repmat([1,2,3,4,5,6,7,8,9,10,10,10,10],1,8); % two decks worth of car...

6 days ago | 0

Answered
Can not convert USHORT MAX to ufix16_Sp01
If you have a slope scaling of 0.01 and a bias of 0, doesn't that mean the max value is 65535*0.01 = 655.35?

6 days ago | 0

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Answered
Using ODE45 for coupled equations
General procedure: Define a variable, let's call it y to match the doc, that will be your state vector. Each element of y corr...

6 days ago | 0

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Answered
please help with work
Use the input( ) function to get the user input. Use the optional 's' argument to get the input as a char string. I'm assuming...

6 days ago | 0

Answered
How to get Matlab Version at Mex Compilation Time?
My MATLAB version code works for me in R2020a: >> mex matlab_version_test.c Building with 'Microsoft Visual C++ 2015 (C)'. ME...

7 days ago | 0

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Answered
Is there a way to use symbolic functions in ode45
Convert it to a function handle so that it can be used with numeric inputs. E.g., >> syms x >> f(x) = sqrt(x) + 2 f(x) = x^...

7 days ago | 1

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Answered
how to write matlab code for physics problem?
You do not explicitly state that acceleration is constant, but I assume that is the case. The equations then are simply vf = v...

7 days ago | 0

Answered
I need help for calculating mortgage for a homework problem
OK, so ask yourself what has to happen every month? You get charged interest and you make a payment, right? And you are told t...

7 days ago | 0

Answered
forward euler for a system of equations
I'm assuming this for j=1:t1:dt was meant to be something like this for j=1:t1/dt

7 days ago | 0

Answered
Splitting a vector into a matrix
result = [x(1:2:end) x(2:2:end)]; or result = reshape(x,2,[]).';

8 days ago | 1

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Answered
Mex file c. Getting different results from matlab
MATLAB stores matrices in column order. E.g., if A is a 2x3 matrix, and p is a pointer to the data area of A in a mex routine, ...

8 days ago | 0

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Answered
I don't know how to prove sin^2(x)+cos^2(x)=1
[cos(x),sin(x)] is defined to be a point on the unit circle, so by definition we have sin^2(x) + cos^2(x) = 1 always. This isn'...

8 days ago | 0

Answered
Using loops in matrix
So your latest post is a really good effort! A couple of things you are missing from the instructions: "create a new variable ...

8 days ago | 1

Answered
How do I use function for a function which has a matrix with variable index?
You don't have a branch for the AR>Max case. If you hit that condition, the output variables will not be assigned. Also, ContA...

8 days ago | 0

Answered
I do not know why am I getting imaginary numbers.
Look at the following for the values of i you are using: log(1-i) E.g., >> log(-1) ans = 0.0000 + 3.1416i

9 days ago | 0

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Answered
multiplying matrix by another matrix element and using it in a command
You can use a loop QT = Q .* reshape(T,1,1,[]); e = zeros(size(QT)); for k=1:size(QT,3) e(:,:,k) = expm(QT(:,:,k)); % fi...

11 days ago | 1

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