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# James Tursa

##### Last seen: Today
3.278 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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Is it a mistake that the function sum?
Welcome to the world of floating point arithmetic. https://www.mathworks.com/matlabcentral/answers/57444-faq-why-is-0-3-0-2-0-1...

alrededor de 12 horas ago | 1

return any angle to (0 to 2pi) range
The short answer: mod(x,2*pi) The long answer for this particular mod operation, is that if you want to get the same answer fo...

1 día ago | 0

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Precision quandaries: why can I print 64 digits?
What you describe sounds like it is just a display issue. Earlier versions of MATLAB on PC machines used a library print functi...

1 día ago | 0

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Grabbing number from array to calculate the numerical derivative
For the version you post, see the diff( ) function along with element-wise divide. E.g., diff(y) ./ diff(x) If that doesn't wo...

2 días ago | 0

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I would advise having your logic figure out what situation you have before you start solving things. E.g., something like if( a...

3 días ago | 0

Numerical solution of ODEs system using ODE45
You've got a 2nd order DE and a 3rd order DE, so the order of your system is 2+3=5, not 6. So your state vector should have 5 e...

3 días ago | 1

Am I doing this right? (a Math formula to Matlab language)
You are on the right track, but have typos in the code due to parentheses issues. A = sum( (x - y).^2 ); B = sum( (x - mean(x)...

4 días ago | 1

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Numerical solution of Higher order differential equation using ODE45 and a m. archice
t is a number, not a symbol. So u = sin(t) is a number, not a symbolic function. So doing diff(u) does diff on a single value,...

4 días ago | 0

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Write an executable script file (m-file) that takes no inputs and returns the displacement and stored energy of a spring system after prompting the user for the 1) input forces (in N) on the spring and 2) the spring constant (in N/m).
To get you started, simply create an m-file with something like this at the front end: F = input('Input the force on the spring...

6 días ago | 0

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How can I add 1 to a particular element in a matrix?
M = your 13x13 matrix M(1,2) = M(1,2) + 1;

7 días ago | 0

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How to determine Simplex using Nelder-Mead Algorithm in all direction?
The Nelder-Mead Simplex Method is an adaptive method that adjusts the lengths and directions dynamically. The vertices could be ...

7 días ago | 0

Question on why tilde cannot return the opposite statement result
Precedence of ~ is hgher than >, so it gets performed first. You need to use parentheses: ~(adultdata.age>50)

8 días ago | 0

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A single column vector or an array, which is faster?
Other things you are doing in your code are likely to dominate run times. We would need to see your particular application to of...

8 días ago | 0

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Matrices and indexing ?!
[LX,LY] = ndgrid(Lx,Ly); z = LX(:)./LY(:) <= 2; LX = LX(z); LY = LY(z); LX and LY contain the number pairs that match the co...

9 días ago | 0

Sort rows of matrix by matching column with another matrix column
E.g., assuming everything in column 31 has a match [~,x] = ismember(A(:,31),B(:,31)); Bsort = B(x,:);

9 días ago | 1

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how to find max value of a function with a for loop
Make e a vector. E.g., for i=1:length(x) e(i) = y(i) - (m*x(i)-b); % <-- Are you sure that isn't supposed to be (m*x(i) +...

9 días ago | 1

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How to solve a system of ODEs and plot the result
This is where you needed to show us the complete code and the complete error message. It is probably complaining about your init...

9 días ago | 0

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precision of calculation with Matlab
Calculators may not use the same floating point representations or arithmetic routines that MATLAB uses, so differences in the t...

9 días ago | 0

How to code for this equation in Matlab
Assuming that f(x) is really supposed to be f(t): f = @(t)exp(j*w*t); But, you will need to have w defined prior to this.

9 días ago | 0

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Mex C file generation Linker library error
Do you already have a zzz.lib file? Normally to get your mexFunction code to link to the library you simply include it as part ...

9 días ago | 0

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rand( ) is a random number generator ... it is supposed to give a different result. doc rand If you want to start over with th...

11 días ago | 1

Help creating an array to hold approx error from a taylor series
Generally, just index into your variable inside the loop: a_values(index) = a_err; If the indexing could be large, you would a...

12 días ago | 0

What is the Aerospace Blockset quaternion convention?

13 días ago | 0

angle between three points (in 3D)?

13 días ago | 0

How to convert char to uint8 and vice versa without changing the underlying data
Simply: c = original char array u = uint8(c); Or u = original uint8 array c = char(u); If you mean you want to reinterpret...

15 días ago | 0

Multiplying each column of a matrix with a specific value
mat=[2,1,0,0;1,0,0,0;0,0,0,1]; % 2D matrix f = [25,5,10,1]; % row vector result = f .* mat; % element-wise multiply with virtu...

15 días ago | 0

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Creating Unit vectors in a loop
Since a complete answer has already been posted, I will post this one using a cell array result which will be much easier to ind...

16 días ago | 1

When i run this code i get error using dec2bin (too many input arguments).
MATLAB is case sensitive. Text (uppercase T) is different from text (lowercase t). In the future, please post the complete erro...

16 días ago | 0