James Tursa

Last seen: Today

4,000 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.

Contact

James Tursa's Badges

View details...

Answered
Can someone explain this Loop?
Of the numbers 1 ... 10 that get produced by the randperm( ) call, only three of them are less than 4: 1, 2, 3. 1 will cause n...

24 hours ago | 0

| accepted

Answered
How to generate unique random integers between 1 to n (with no possibility of Sequence)
If 1:n is the only sequence you don't want, just use randperm(n) and reject the one case you don't want. I.e., if you get it the...

4 days ago | 0

Answered
How do solve four variables with one equation using Runge-kutta?
You have three state variables, namely v, lc, and z. But you only have code for updating v. You need code for updating lc and ...

4 days ago | 1

| accepted

Answered
A code and plot a graph for a projectile motion of a ball
Your main problem is that you don't have enough state variables. You have these two equations: x'' = 0 y'' = -g That's two 2...

4 days ago | 0

Answered
Converting Struct field to array
Does this do what you want? MyMatrix = vertcat(MyStruct.Field);

6 days ago | 0

| accepted

Answered
Trying to build a new nx4 array from an existing nx4 array using logical values
Assuming quatAB is a standard numeric matrix, use your logical variable for the first index and colon for the second index: m =...

7 days ago | 0

Answered
How do I combine a structure array into one structure
F = fieldnames(A); n = numel(F); C = arrayfun(@(i)vertcat(A.(F{i})),1:n,'uni',false); FC = [F';C]; B = struct(FC{:});

7 days ago | 0

Answered
Finding optimal value for x
You could try this function to get numeric values for local minimums: https://www.mathworks.com/help/matlab/ref/fminsearch.html...

8 days ago | 0

Answered
Using fprintf to save a matrix changes the order of my matrix
MATLAB stores 2D matrices in column order. That is, the numbers in your matrix are stored in memory in this order: 0, 1, 2, 3,...

8 days ago | 0

Answered
please help me to convert c code into matlab code for partial shading of solar panel using equilibration algorithm
In addition to what @Image Analyst has written, I would advise turning this into a function with p1, p2, p3 as input arguments a...

8 days ago | 0

Answered
Difference between using single quotes ('xyz') and double quotes ("xyz") in formatspec
In MATLAB, single quotes ' ' are used to create char type variables, and double quotes " " are used to create string type variab...

14 days ago | 0

| accepted

Answered
Error in ode45 while doing numerical integration
The function handle you pass to ode45( ) needs to have a (t,y) signature. E.g., [t,y] = ode45(@(t,y) myode(t,gt,g), tspan, ic, ...

14 days ago | 0

Answered
How to multiply higher order matrices?
You may need to permute your arrays first to get your desired 2D slices in the first two dimensions. A = whatever B = whatever...

22 days ago | 2

Answered
Using matrix to index another matrix?
Does this do what you want: x = sub2ind(size(B),(1:size(A,1))',A(:,1),A(:,2),A(:,3)); Output = B(x);

22 days ago | 0

| accepted

Answered
Equivalent of c++'s NULL or python' s None in MATLAB
This will probably depend on how these are used downstream in your code and whether you have arrays of them to deal with. If th...

26 days ago | 1

Answered
X Y Z angles of a D20 (icosahedron) for gravity projection
If you have the 3D normal vectors, then all you need to do is take the dot product between them and the "flat" face normal vecto...

26 days ago | 1

| accepted

Answered
modify a row of an array within a function
This can sometimes be done inplace depending on how you write the function and how you call the function. One requirement is yo...

28 days ago | 0

Answered
Operator '-' is not supported for operands of type 'function_handle'.
You are using u as both an input argument and a global function handle function A3 = odeFun(t, u) <-- input argument global R...

29 days ago | 0

Answered
Solve a system of 3 second order ODE
You will need to change your scalar equations to vector equations, and you will need to change your derivative function to a vec...

29 days ago | 0

Answered
Need to speed up the generation of random numbers.
You could over generate a large matrix and then pick off the number of elements you need later. E.g., C = rand([5 size(A)]); T...

29 days ago | 0

Answered
How do i create a large matrix with a formula?
N = 1000; a = 2 * pi * f * T * (0:N-1)'; x = [cos(a) -sin(a)];

29 days ago | 1

Answered
Matrix multiplication to get covariance matrix
@Tintin Milou MATLAB variables do not have a "symmetric" attribute flag that I know of. Just because you create a variable that...

29 days ago | 0

Answered
Why can't complex integer arithmetic be done?
I think the main reason for disallowing integer array arithmetic in MATLAB is because of the ambiguity caused by the max(min( ))...

1 month ago | 1

Answered
How can I split C/C++ Code in multiple files and still use MEX
Use the -c option to compile the B and C stuff to produce only object files without any linking: mex -c B.c C.c Then compile y...

1 month ago | 1

| accepted

Answered
Matrix multiplication. Trying to get scalar solution
Those should be matrix multiples, not element-wise multiplies. Remove the dots. E.g., top=nMode * M * u0; bot=nMode * M * nM...

1 month ago | 0

| accepted

Answered
Adapt RK4 ODE Solver from first order to 2nd order
Try this for starters yt = zeros(numel(y0),length(h:tfinal)); %Memory Allocation And then maybe this is what is intended for i...

1 month ago | 0

| accepted

Answered
Error using vertcat Dimensions of arrays being concatenated are not consistent.
You have a mismatch in the number of arguments. E.g., this [V,y] = ode45(@(~,y) fun(del_h1,del_cp1,cp1),Vspan,y0); should be ...

1 month ago | 0

Answered
Replacing matrix n column values
E.g., temp = A(:,70:80); temp(temp<0) = 0; A(:,70:80) = temp;

1 month ago | 1

| accepted

Answered
Solving an overdetermined system of linear equations
Since you can simply plug in those values to verify that they satisfy all four equations, the conclusion would be that you have ...

1 month ago | 0

| accepted

Answered
How to create a cell array with binary numbers?
Your pop variable has 1000x11 = 11000 elements. Your for-loop only assigns values to 1000 of those elements (the first column)....

1 month ago | 0