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James Tursa


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3.827 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
Array Cascade Addition calculation
One way using implicit array expansion: D = A(:) + reshape(B,1,[]) + reshape(C,1,1,[]); Your results are the elements of D. I...

etwa 22 Stunden ago | 0

Answered
Getting NaN in Rung-Kutta 4, Simulation of 10 planets
OK, I will take a look at things. But your attempt at "simplifying" your numbers by using a custom distance unit and apparently...

etwa 22 Stunden ago | 0

Answered
Fill in a data vector into a preallocated zeros matrix
m = reshape(v,500001,4);

ein Tag ago | 0

| accepted

Answered
Multiplication of 2 sets to get all possible outcomes
This is a simple outer product: c = a' * sin(b);

2 Tage ago | 0

Answered
array indices and bisector method
It is not clear what z is supposed to be used for in these lines: z(xL) = PDFunction (m,k,xL); z(xU) = PDFunction (m,k...

2 Tage ago | 0

Answered
Matrix multiplication accuracy problem
This difference is this: R0=A'*A; In the above expression, you are using the exact same matrix A on both sides of the operatio...

2 Tage ago | 1

| accepted

Answered
multiplication of multiple type matrices
Matrix multiplication is associative, so the order of the multiplication doesn't matter mathematically. You might get small dif...

2 Tage ago | 0

Answered
Advantages of mwsize (Cross-Platform Flexibility)?
"Furthermore, a question arose regarding the 'MATLAB Support for Interleaved Complex API in MEX Functions'. Which API is preferr...

2 Tage ago | 0

Answered
How do i transform a second grade ODE into coordinates?
Looks like motion is restricted to be on the x-y plane, so r is 2D. You have a 2nd order ODE in a 2D frame, so that means you h...

5 Tage ago | 1

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Answered
Runge-Kutta 4 implemetation blowing up
s(:,i+1) = s(:,i) + 1/6*(k1 + 2*k2 + 2*k3 + k4); % changed s(:,i+1) to s(:,i) on rhs

5 Tage ago | 0

Answered
Need help with error checking
There are various ways to code this, but keeping the same basic architecture you have chosen you could do this: while( true ) ...

5 Tage ago | 0

Answered
Assignment has more non-singleton rhs dimensions than non-singleton subscripts ERROR IN FOR LOOP
x(:,i+1)=x(:,i)+A*x(:,i)+B*u(:,i); % changed u(i) to u(:,i)

7 Tage ago | 0

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Answered
Runge Kutta integration problem - NaN result
You may have a stiff DE and you can't use RK4 with a fixed step size. What happens when you call ode45( ) instead of ode15s( )?...

9 Tage ago | 0

Answered
Calculating the height of a liquid in a sphere using secant method
You need to use a function that is 0 at the h you are looking for. So you need that 30 in your function handle. E.g., func = @(...

10 Tage ago | 0

| accepted

Answered
Not enough input arguments
You need to call the function with the N input you just got from the user. E.g., disp(quiz6_func1(x,N))

10 Tage ago | 1

| accepted

Answered
ode45 function array error
You have tm(1) = 0, so using tm(1) as an index is invalid: tm=[0 30 etc... : for i=1:length(tm) : Ss_in(tm(i):end)...

10 Tage ago | 0

Answered
Is FORMAT DEBUG still any useful?
Strange behavior and probably deserves a bug report. E.g., R2019a: >> x = 1; >> y = x; >> x = x + 1; >> format debug >> y...

10 Tage ago | 0

| accepted

Answered
Precision (decimal digits) are very low and digits(32) does not help.
This is likely just a display issue and you don't need the Symbolic Toolbox. MATLAB does regular calculations in full double pr...

10 Tage ago | 0

Answered
Consecutive subtraction of the entries of a vector
If A is a row vector: B = [A(1) diff(A)]; If A is a column vector: B = [A(1);diff(A)];

11 Tage ago | 0

| accepted

Answered
generate random number with total sum is 10
Not sure from your wording if you want the row sums to be 1 or 10. If it is 1, then r = rand(6,1); r(:,2) = 1 - r(:,1); Modif...

11 Tage ago | 0

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Answered
when does changing variable's value affects its structure address?
In addition to what Walter has written, I would point out that all of the rules for variable creation, assignment, and sharing h...

11 Tage ago | 0

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Answered
Replace the numbers in an array
A(~isnan(A)) = B;

12 Tage ago | 1

Answered
Vector ODE using forward Euler method
Also your main code should look something like this: g = 9.8; mu = 0.5; [t,y]=ode45(@(t,y)rhs_1(t,y,g,mu),[0 100],[0.1; 0]); ...

13 Tage ago | 1

Answered
unique function return value of duplicate vector entry
Why can't you just use ind1 and ind2? E.g., V1_1 = V1_1(ind1); V2_1 = V2_1(ind1); V1_2 = V1_2(ind2); V2_2 = V2_2(ind2);

16 Tage ago | 0

Answered
Insignificant modification of code leads to NaN
Think about what is happening with this loop: for i = 1:num_iterates x = A*x; R(:,i) = x/norm(x); %%%% Problem Line %...

25 Tage ago | 1

| accepted

Answered
Skip instance of a loop with error
Something like this: try fn = x+y+z; %The function is just a representation. I am actually performing a Fi...

26 Tage ago | 0

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Answered
Performance of applications that are developed in MATLAB versus C++/C
Any such comparison will depend on exactly what computations are in question. A general comparison of languages probably isn't ...

26 Tage ago | 2

Answered
Numerical Integration by Matlab
Hint: You might look here: https://en.wikipedia.org/wiki/Normal_distribution Knowing that the integral of the Normal density f...

26 Tage ago | 0

Answered
Does MEX compiler (and the associated shared files) automatically ship with all MATLAB distributions of any license type?
Mex routines are not guaranteed to be compatible between different versions of MATLAB, for the very dependency reasons you alrea...

26 Tage ago | 1

| accepted

Answered
function call returns "index (1.2): subscripts must be either integers 1 to (2^63)-1"
You are missing a multiply operator. There is no implied multiplication in MATLAB with the 2( combination. E.g., u_1 = @(y) ...

28 Tage ago | 0

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