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James Tursa


Last seen: 1日 前 2007 以来アクティブ

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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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...

1日 前 | 1

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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...

1日 前 | 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...

3日 前 | 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...

15日 前 | 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 ...

15日 前 | 0

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

16日 前 | 1

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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 ...

16日 前 | 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)

18日 前 | 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...

19日 前 | 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 ...

24日 前 | 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 ...

約1ヶ月 前 | 0

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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...

約1ヶ月 前 | 1

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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...

約1ヶ月 前 | 1

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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 ...

約1ヶ月 前 | 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

約1ヶ月 前 | 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...

約1ヶ月 前 | 0

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numerical integration with recursive trapezoid rule
Some issues are immediately apparent. First, you don't reset S=0 inside the while loop. Isn't S supposed to contain only the a...

約1ヶ月 前 | 0

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Store every N columns in a Matrix to a new Matrix
Don't create a bunch of new matrices with hard to use names downstream in your code. Instead, simply reshape your matrix and the...

約2ヶ月 前 | 0

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MEX file always crashes when I run it
In the MATLAB code you have this: np=single(np); Then inside the Fortran gateway routine you have this: mwPointer xr, yr, n ...

約2ヶ月 前 | 0

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How can I reshape a matrix this way
a=[-0.26,0.23,0.033,0.1,-0.39,0.30;0.30,-0.39,0.10,-0.26,0.03,0.23;-0.03,-0.13,0.16,0.33,-0.16,-0.16] b=[-0.26,0.23,0.033;0.1,-...

約2ヶ月 前 | 0

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Matlab while loops with equations
You should probably go through the online tutorials for learning MATLAB. But I will give you an outline to get started: toleran...

約2ヶ月 前 | 0

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i need to find error in code because I it's increasing but it should be decresing
You need to use all the derivatives at the first point to propagate for the initial guess at the second point. I.e., these lines...

約2ヶ月 前 | 0

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t = 2 s, i = √−1, and 𝜔=120π rad/s. Evaluate the following using MATLAB? Hint: exp(n) is used in MATLAB to evaluate en. (a) e−2𝑡𝑐o𝑠 (𝜔𝑡)
I am guessing that the original expression shown is supposed to be interpreted as: Then take the hint at how to evaluate the ...

2ヶ月 前 | 0

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Why is my projectile motion code only working at certain input angles.
Drag depends on current velocity, not initial velocity. So you need to recalculate V at each step. E.g., Vx = Vx_new; Vy = Vy_...

2ヶ月 前 | 0

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Sine equation in Euler Method ODE
You've only got one scalar differential equation, so I don't understand why you think you need two variables x and y along with ...

3ヶ月 前 | 0

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subtract matrix from vector
Just learn how to use indexing and element-wise operators. From your language, here are the pieces: subtract - the first thre...

3ヶ月 前 | 0

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How can I create arrays with different names using loop?
Don't embed numbering into the variable names. This will make the variables hard to use downstream in your code. Use cell arrays...

3ヶ月 前 | 0

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How to subtract each column of a matrix from a column vector?
Just do a usual subtraction and let MATLAB implicit expansion kick in: M = your matrix v = your column vector result = v - M;...

3ヶ月 前 | 0

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Simple mex file crash?
You need to create the output variable yourself. plhs[0] doesn't exist until you create it, thus this line crashes: outData = m...

3ヶ月 前 | 0

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Simulating Projectile with Matlab
You don't show us both methods (with and without drag) so we can't compare them. I presume you simply set k=0 for the case witho...

3ヶ月 前 | 1

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