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James Tursa


Last seen: Today Active 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
Write multiple variables from a function
Maybe something like this does what you want, with each qq1 and qq2 2D page results in the first two dimensions. [m n] = size(s...

3 Tage ago | 0

Answered
In an assignment A(I) = B, the number of elements in B and I must be the same.
" And in the work space y2 is 3x1 and d is 1x1 " Then d - y2 will be 3x1. You can't assign a 3-element vector to a 1x1 scalar w...

4 Tage ago | 0

Answered
After the if statement is ran why is the answer 10?
A=1; : if A<0 A is not negative, so the body of the if-test never runs.

9 Tage ago | 0

Answered
Solve nonlinear 2nd order ODE numerically
You can look at the examples for ode45( ) here: https://www.mathworks.com/help/matlab/ref/ode45.html?searchHighlight=ode45&s_ti...

11 Tage ago | 1

Answered
The input function does not work well
Pass in a vector using the square brackets. E.g., binary_to_decimal([1 0 0 1 1 0])

12 Tage ago | 0

| accepted

Answered
Concatenate logical/numerical arrays element wise
Here is one way: % Generate sample data H{1} = rand(2,3)<0.5; H{2} = rand(2,3)<0.5; H{3} = rand(2,3)<0.5; Hc = cat(3,H{:}) ...

12 Tage ago | 2

| accepted

Answered
What is the difference between " while 1" and "while true", Should I use one over the other?
1 is a double class scalar and true is a logical class scalar, so the check for "non-zero" is slightly different for each even t...

14 Tage ago | 0

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Answered
I have a 4 Dimensional Matrix and i want to get its transpose
Maybe this does what you want, which is transpose the first two dimensions: permute(val,[2 1 3 4]) Or you could use this funct...

19 Tage ago | 0

Answered
How to multiply a 3d array with a 2d matrix?
It would be best if your 2D pages were the first two dimensions. That way the 2D pages are contiguous in memory and you can use ...

etwa ein Monat ago | 1

Answered
Error in concatination in binary values
c1=[8 14 10 9 6 3 2 7 6 11 6 3 13 15 6 0]; NewR = c1(1:2:end)*16 + c1(2:2:end)

etwa ein Monat ago | 0

Answered
Increased time for setting elements in sparse matrix
Every time you change the elements of a sparse matrix, MATLAB has to deep copy all the existing elements to a newly allocated ch...

etwa ein Monat ago | 1

Answered
How to run a Matlab file which uses functions from .c and .dll files?
It appears that this may be an older mex routine? Is there a "mexFunction" in the c file? If so, maybe you can just recompile it...

etwa ein Monat ago | 1

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Answered
Unable to perform assignment because the left and right sides have a different number of elements.
Why are you replacing the sin(y-c) term with approximations? Why haven't you just programmed it as is? It appears you have done ...

etwa ein Monat ago | 0

Answered
Applying runge kutta for coupled equations
What are and ? Why don't they have differential equations associated with them? Can you give more details about this? Also, it...

etwa ein Monat ago | 0

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Answered
How to create a loop on function handle
Isn't this just a standard matrix*vector multiply? E.g., XI = @(xi) xi - (y(i,:) + A*((t(i)+c*dt).*xi)*dt); Note that this fun...

etwa ein Monat ago | 1

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Answered
Index Matrix A and Matrix B Problems
You can use logical indexing: B(A==1) = 0; You can use a loop for this also, but you would have to show us the code you used b...

etwa ein Monat ago | 1

Answered
Whole derivation of two variable differential function
Please show the code you are using. y' means derivative of y with respect to x, not derivative of y with respect to y. You sho...

etwa 2 Monate ago | 0

Answered
How do i compile multiple fortran code from matlab command
To pass variables from MATLAB to your Fortran code you would typically do the following: Write a single gateway routine in a se...

etwa 2 Monate ago | 0

Answered
Updating Sparse Matrices every Time-Step Efficiently
To specify the sparse matrix size when creating it, use the following syntax: sparse(I,J,K,m,n) where m is the number of rows ...

etwa 2 Monate ago | 0

Answered
how to move a row
result = M([1:400,801,401:800,802])

etwa 2 Monate ago | 1

| accepted

Answered
How to set specific size of a figure with exportgraphics?
This doesn't answer your question about controlling exported sizes, but you might be interested in the following export_fig FEX ...

etwa 2 Monate ago | 0

Answered
Renaming the variabel while Symbolic to function handle conversion with matlabFunction
You could keep your existing code and create another function handle: funcv = @(A,xdata,ydata)func(A(1),A(2),xdata,ydata)

2 Monate ago | 0

Answered
Making an Array out of another Array if conditions are met
You don't need a for-loop for this. The best way is to use logical indexing. See this link: https://www.mathworks.com/help/matl...

2 Monate ago | 0

| accepted

Answered
How to remove February 29th for leap years in a daily time series over 43 years?
To get rid of the leap days, you can use evenly spaced indexing since the number of days between leap days is constant for your ...

2 Monate ago | 0

Answered
I would like to write a for loop to store all values of y when A=1,2,3,4,5. into a variable y1,y2,y3,y4,y5 respectively. Any help will be greatly appreciated. Thanks
No loop needed, and no need to create multiple variables to hold results. Just use implicit array expansion and hold results in ...

3 Monate ago | 0

| accepted

Answered
Index in position 1 is invalid. Array indices must be positive integers or logical values.
Looks like you changed the definition of what f_m is in your code. In these lines f_m appears to be an array intended to hold va...

3 Monate ago | 1

Answered
What does A(2:4) = [ ] do if A is a 3x3 matrix?
This is linear indexing. Even though the variable is a 2D matrix, MATLAB allows you to index into it using only one index. The l...

3 Monate ago | 1

Answered
error using function code
Create a file called lettergrade.m somewhere on the MATLAB path (e.g., in your working directory) edit lettergrade.m Copy all ...

3 Monate ago | 0

Answered
dynamic naming of structures
Would it be acceptable to use x as a dynamic fieldname instead of the top level variable name? E.g., v.(x).a v.(x).b

3 Monate ago | 1

Answered
How can I define an array of sparse matrix? (both for GPU and CPU)
For CPU, you can use the ndSparse submission by Matt J on the FEX: https://www.mathworks.com/matlabcentral/fileexchange/29832-n...

3 Monate ago | 0

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