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James Tursa


Last seen: 1일 전
3,954 2007 이후 총 참여 횟수

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 can I solve a system of ODE's, in which the equations have a dependency on time, as well as the other ODEs?
Just code it up as it appears using a 3-element state vector, where the elements are defined as follows y(1) = x y(2) = y y(3...

6일 전 | 0

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How to improve the speed of large matrix addition?
If you are generating a new matrix C each time, then you are essentially doing two things: (1) Copying all the elements of A in...

6일 전 | 0

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Dealing with very small or very large numbers
I guess the obvious suggestion is to work in units of nanometers or maybe picometers instead of meters. Can you do that?

8일 전 | 0

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How to use if statement in function?
Add this code to the top of your function: if( N <= 0 ) error('N needs to be > 0') end That being said, your loop probab...

9일 전 | 1

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How to build a quaternion from a normal vector?
If you have the Aerospace Toolbox, you could do the following n = 1x3 unit normal vector a = angle to rotate in radians v = 1...

9일 전 | 0

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Runge-Kutta 2
Normally one would plot the position, not the velocity. So I would have expected you to plot the "1" index of your solutions. ...

9일 전 | 0

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Double Variable Second order Differential Equation
Just write a derivative function using four states instead of two. The states will be x, y, dxdt, and dydt. The derivitives of...

9일 전 | 1

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How can I divide each element of a vector by each of the elements of another vector in MATLAB?
Assuming a and b are both column vectors, you can use automatic array expansion by transposing one of them and using element-wis...

10일 전 | 0

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"Array indicies must be positive integers" error
You can't have 0 or fractional indexing in MATLAB. Take this section of code for example: for t = 0:1:200 U(0,t) = ui; ...

10일 전 | 0

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what is the difference between the 2 codes ?
zeros([2,2]) passes one argument, a 2-element vector [2,2]. zeros(2,2) passes two arguments, the scalars 2 and 2. The result i...

10일 전 | 0

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Getting all Permutations of a 18+ integer vector
The number of different permutations of a vector of size n is n! (n factorial). So what you are attempting has these many possi...

10일 전 | 0

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Calculating a matrix with a specific form
You could rearrange the equations, isolate m(1), m(2), and m(3) and solve for them directly. E.g., rearrange the equations to f...

11일 전 | 2

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Combine logical arrays into one array
L = L1 | L2 | L3 | L4;

11일 전 | 0

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How to vectorise code involving matrix multiplications with vectors
See this link: https://www.mathworks.com/matlabcentral/answers/776812-how-to-vectorize-a-b-operation-on-slices-of-3d-matrices?s...

11일 전 | 0

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What is the corect code for writing an error message when a user inputs an array instead of a scalar value?
Several ways to test for a scalar. E.g., if( ~isscalar(x) ) error('Input is not a scalar'); end or if( numel(x) ~= 1 )...

11일 전 | 0

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Calculating and and recording a vector during each iteration of a "while" loop.
E.g., using a counter to store all of your iteration data in a cell array and then post process this: k = 1; % the counter Rce...

11일 전 | 0

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Trying to separate Quaternion coefficients into array.
Use the double( ) function to convert to numeric array, then use regular indexing. E.g., try this function g = actfun(q) ...

11일 전 | 1

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quat2eul is giving me a strange result
Maybe all you have to do is add 2*pi to all results that are less than -pi to get things how you want.

16일 전 | 0

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Handling Inputs mex function
The prhs[ ] variables are of type pointer to mxArray ... you cannot use simple native C conversions with them. You must use som...

18일 전 | 0

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How can I fix this error?
Delete the extra closing parentheses. I.e., delete the paren where the red underline is.

19일 전 | 0

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Undefined function or variable t
Put this code in a separate file called Math.m % file Math.m function dxdt=Math(t,x1) % function name x=x1(1) y=x1(2) z=x1(...

19일 전 | 0

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Generating a 4th order Runge-Kutta Integrator solver for the motion equation.
ode45( ) is not well suited to the orbit problem since the integration errors can systematically build up over time. You can tr...

19일 전 | 0

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ODE45 function for 3 Variables
This y0 = [0;0;0;0]; and this zF = 0; means that your derivative function will evaluate to 0 exactly, so the solution is 0 e...

19일 전 | 0

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Can anyone help?
Hint: Look at the results of this operation, and I think you can figure it out from there: x = [2;3;4]; % column vector y = 0:...

약 1달 전 | 0

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How binary Random number generation upto n nodes ?
Here is how to get your stated desired output, but this is not random at all: r = dec2bin(0:(2^L-1)) - '0';

약 1달 전 | 0

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Undefined function or variable 'bisection'.
From the error message, it looks like you are calling the function using the name "bisection", but the actual name of the functi...

약 1달 전 | 0

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ODE45 in 3 dimensions with 6 initial conditions
I find it easier to keep the position elements together, and the velocity elements together, in the state vector. So I would de...

약 1달 전 | 1

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Generate a Runge-Kutta Integrator solver for the orbital motion equation, when given the initial conditions. Execute for 500 seconds.
First, I find it easier to keep the position elements together, and the velocity elements together, in the state vector. So I w...

약 1달 전 | 1

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Runge-Kutta method, cannot produce the correct graphs
You need to index x in your calculations. E.g., q1 = f(x(i),y(i)); q2 = f(x(i)+h, y(i)+h*q1); You should init...

약 1달 전 | 0

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Working with an equation and variables from user.
You can construct a function handle as follows: f = str2func(['@(x,y)' str1]); You can then use this function handle to evalua...

약 1달 전 | 0

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