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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...

5 days 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...

6 days ago | 0

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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.

11 days ago | 0

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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...

13 days ago | 1

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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])

14 days ago | 0

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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{:}) ...

14 days ago | 2

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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...

16 days 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...

21 days ago | 0

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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 ...

1 month ago | 1

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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)

1 month 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...

1 month ago | 1

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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...

1 month 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 ...

1 month ago | 0

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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...

1 month 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...

2 months 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...

2 months ago | 1

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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...

2 months ago | 0

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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...

2 months ago | 0

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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 ...

2 months ago | 0

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

2 months ago | 1

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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 ...

2 months ago | 0

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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 months ago | 0

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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 months ago | 0

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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 months ago | 0

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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 months ago | 0

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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 months 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 months 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 months ago | 0

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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 months ago | 1

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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 months ago | 0