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James Tursa


3,130 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
How to get field value from a struct as a variable in order to use in a code?
Depends on your downstream code whether this is really worth it, but simply e.g. x = yourstruct.x; y = yourstruct.y;

3 days ago | 1

Answered
Attempting to have a series for sin stop summing when the precision is correct
Inside the sinser function, you never set p to a vector ... it is always just a scalar. If you want to return all of those inte...

3 days ago | 0

Answered
generate unit vectors based on matrix size
Why not just V(1,2) = 1; Or if you really need to explicitly set those 0’s then start with V(:,2) = 0; followed by the above...

5 days ago | 0

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Answered
mod gives incorrect result
See this thread: https://www.mathworks.com/matlabcentral/answers/338182-how-to-get-mod-of-large-numbers

5 days ago | 1

| accepted

Answered
eulers improved method code error
s2=F(x+h/2,y+h*s1/2); %% is it correct for modified euler If "Improved" Euler's Method means "Modified" Euler's Method as your ...

5 days ago | 1

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Answered
Unable to perform assignment because the indices on the left side are not compatible with the size of the right side. What does this mean?
Look at this line: Segment(n_start)=data(n_start:(n_start+ window_size-1)); and simply plug in the numbers for the first itera...

5 days ago | 1

Answered
Getting an error with the ODE45 function.
You've got your calling code mixed in with your derivative code. You need to code this differently. E.g., one way: In a file c...

6 days ago | 0

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Answered
Runge Kutta method computational cost
Side Note, You should not be calculating f(x(k),t(k)) twice in your 2nd order method. You should be doing it like your 4th orde...

9 days ago | 1

Answered
Mex -largeArrayDims in Linux
You didn't give it the LAPACK library to link to, so there is no dgesv_ function, hence the error. You need to take this: lapac...

9 days ago | 0

Answered
Can MEX BLAS library be used for native double matrix in C?
Two problems: 2D matrices are stored column-wise by MATLAB and is assumed by the BLAS and LAPACK routines also. So this: ...

10 days ago | 1

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Answered
How to save ode45 outputs in a loop?
Don't use a loop. Just call ode45 once and it will give you the entire results in T and Y. [T,Y] = ode45(dydt, t, [y0, dy0]); ...

11 days ago | 0

Answered
Creating vectors by rand() and looping it
Good start, but do this to save the ceil function result back into vector: vector = ceil(vector); For the next part you need a...

17 days ago | 0

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Answered
How do I pull a value out of a different equation @ a specific value
[Tmin,k] = min(T); Dt = D(k);

17 days ago | 0

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Answered
Multiplying every secound element in a vector with -1
Or yet another of the zillion ways vny = v; vny(2:2:end) = -vny(2:2:end);

17 days ago | 1

Answered
Too many output arguments.
Why not just c = 2*x; d = 4*y;

18 days ago | 0

Answered
How to call all arrays that start with the name "CV_"?
Don't do that. See this post for reasons why: https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-sh...

18 days ago | 0

Answered
Trying to create a simple function Matlab gives me an error message
Put your vecout( ) function code in a separate file called vecout.m

18 days ago | 0

Answered
Hi guys, help me, please!
MATLAB indexing is 1-based, not 0-based. You will need to adjust your indexing: a(1) = 1; a(2) = 0; : etc

18 days ago | 0

Answered
Dimensions of arrays being concatenated are not consistent.
If they are all row vectors, then I would think something like this: Total_No_cells_r = [Total_No_cells_r, total_cellcount_r]; ...

18 days ago | 0

Answered
Extract integer number from a cell array.
You could do this: C = your cell array of strings, some containing numbers d = str2double(C); d = d(~isnan(d));

19 days ago | 0

Answered
Why is the inv function not working in this code (simple)
Best to put commas in your matrix difinition so that the parser doesn't inadvertently combine things that you didn't want. E.g.,...

19 days ago | 1

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Answered
(ODE45) Unable to perform assignment because the left and right sides have a different number of elements
It might be simpler to have separate files for this. Put this code (and only this code) in a file called HW4_matlab.m %% Solvi...

19 days ago | 0

Answered
Precision in calculation of large digits
You need to convert to vpa first so that the factorial calculation is done with extended precision. factorial(vpa(97))

19 days ago | 2

Answered
Attempting to completely fill out an array(6,7) with 1's and 2's for connect4
Maybe you could explain what your code is supposed to be doing. Commenting the code would be great. But if you just want a boa...

23 days ago | 0

Answered
not enough argument input
You need to put your function code into a file called dew_point.m Then you need to call your function with inputs, e.g. T = so...

23 days ago | 1

Answered
Can someone help me Create a function called that will automatically generate an array where the elements in the array are the sum of the indices? i am lost on this.
If I understand your description correctly, the magic( ) function has nothing to do with your assignment. You are simply asked t...

23 days ago | 1

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Answered
Data arithmatic addition with single precision
Floating point operations will often yield slightly different results if you change the order of operations. This is to be expec...

24 days ago | 0

Answered
How to locate the index of the maximum value in a given range
Use the 2nd output of the max function: [p,i] = max(y); p is the max value, i is the index of the max value t(i) is the value...

24 days ago | 0

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Answered
Change all elements in 2nd column to 3
vArr(:,2) = _____; % <-- you fill in the blank

24 days ago | 0

Answered
Create array Arr with 5 rows and 4 columns with each element = 5
Yes. Replace all of your numbers with 5 and you will have it. E.g., Arr = [5 5 5 5; etc. This is the hardest way to accomplish...

24 days ago | 0

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