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James Tursa


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3.833 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
Multiple names for a single variable.
There are no "variable pointers" in MATLAB, so no generic alias capability as you would probably want. Other options to conside...

alrededor de 13 horas ago | 2

Answered
How to locate and link with the exact same Intel MKL that MATLAB is shipped with?
On my Win64 machine I find them here [matlabroot '/extern/lib/win64/microsoft'] and here [matlabroot '/extern/lib/win64/mingw...

alrededor de 15 horas ago | 0

Answered
Use Gaussian Jordan Elimination to convert binary matrix to All zero Matrix
Here is the code, which implements your stated algorithm directly. The input n is the known size of the upper triangular block ...

1 día ago | 0

Answered
MATLAB Smallest Integer in floating point number system
IEEE double has a 52-bit mantissa, plus there is a hidden bit, so effectively 53-bit mantissa. So you can exactly represent all ...

1 día ago | 0

| accepted

Answered
Adding 32 to specific indices in a vector
x(y) = x(y) + 32;

1 día ago | 0

| accepted

Answered
Find elements in vector that satisfy condition
X = your big matrix k = column number you want to examine value = some number you are looking for idx = (X(:,k) == value); % ...

1 día ago | 0

| accepted

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...

5 días ago | 0

| accepted

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...

5 días ago | 0

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

6 días ago | 0

| accepted

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

6 días 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...

6 días 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...

6 días 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...

6 días 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...

7 días 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...

9 días ago | 1

| accepted

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

9 días 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 ) ...

10 días 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)

12 días ago | 0

| accepted

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( )?...

14 días 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 = @(...

14 días 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))

14 días 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)...

15 días 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...

15 días 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...

15 días 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)];

15 días 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...

15 días ago | 0

| accepted

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...

16 días ago | 0

| accepted

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

16 días 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]); ...

18 días 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);

21 días ago | 0

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