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Sign of imaginary value changes after converting to array
Here is what I get: >> a = 2 + 1j; >> b = 1 + 3j; >> z1 = a*b z1 = -1.0000 + 7.0000i >> z2 = b*conj(b) z2 = 10 >>...

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How can I plot the function y = e^(-2x^2) * cos(4pi*x - 1.5)?
Pick a range for x. E.g., x = 0:0.01:2; y = exp(-2.*x.^2) .* cos(4.*pi.*x - 1.5); plot(x,y)

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Where in my code using runge- kutta four step method did I make a mistake?
Type the following at the command line: edit rk4singlestep.m Then copy your code into that file and save it.

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Projectile motion without drag
You don't define the Vx(k) value before using it, hence the error. Since your Vx values don't change you can fix this error by ...

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Define x,y,z and evaluate them.
You can define variables simply by typical assignment. E.g., x=5; y=4; etc. You can use * for multiply and ^ for exponentiat...

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Fortran MEX returns only some elements of output array.
The problem isn't using allocatable variables ... MATLAB mex functions can handle that just fine. The problem is that you are u...

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System of ODEs with interdependent variables
I would advise writing a derivative function for this. E.g., dydt = myderivative(t,y,gna,gk,gl,Vna,Vk,Vl,I) V = y(1); n = y(...

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Outlet Limit: water depth and flow rate
You are being asked to write a function that takes H and Q as inputs, and outputs the diameter D. So the function outline would...

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writing out a quadratic
Use the element-wise operators that include the "dot" (such as .^ instead of just ^), and use the multiply operator * between th...

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How can I select three random sample of a matrix with minimum separation between samples?
A rejection method is straightforward. Simply make your selections in a forever loop until you get something that works. The a...

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Cell to matrix under new variable
Do not do this! You are taking a method of storing your data that is easy to maintain and access (e.g., in a loop) and proposin...

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Adding 2 matrices together in matlab, got errors instead
result = [a,b];

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Reduce size of multidimensional array
One way using summing: result = squeeze(sum(your_array,3));

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Euler's code for multiple ODEs
You have two states, so your result should have two values per step. So this code: y = zeros (1,N); % Initialize the Y vec...

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Runge-Kutta 4th Order on a 2nd Order ODE
All of your derivatives should be with respect to the independent variable x. In the context of your problem, dy/dz does not ma...

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Something wrong with quat2angle() function?
I agree that this looks like a bug, and you should submit a bug report to TMW for this. I ran it in R2017a and R2020a and both ...

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want to solve (d^2 y)/(dx^2 )+dy/dx-6y=0 using 4th order Runge-Kutta method with y(0) = 3 and y’(0) = 1
Change your function handle from this f = @(x) (dy^2)/(dx^2 )+dy/dx-6*y; to this f = @(x,y) [y(2);-y(2)+6*y(1)]; The last pa...

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How to use Bisection Program to locate Roots of given function
If the derivative depended only on the time t then your strategy for finding the maximum/minimum points would be a good one. Ju...

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ODE45, ODEfunc question
What you might want to do is pass a function handle for this. E.g., in your calling code create the function handle: C1 = what...

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Runge-kutta 4th order Method Help
All of your F's need to be functions that operate on the current full states. E.g., take this one F_C1 = (xc*yc*((C1.*R1)./(R1...

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Difference/usage of mwIndex, mwSignedIndex and mwSize in mex C-code
MATLAB provides multiple libraries that mex code links to. There can be both 32-bit and 64-bit versions of functions in the var...

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Matrix index is out of range for deletion.
You should step through this with the debugger to see what is going on. I.e., click to the left of a line and then run your cod...

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How to stack k copies of a matrix
B = repmat(A,1,1,k);

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how can i find the co-ordinates of intersections of two lines?
Suppose you have two line equations: 2x + 3y = 1 3x - 5y = 11 Then you can form the matrix A and the right hand side vector b...

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difference between euler angles and rotation vector
The rotvecd( ) function gives a scaled rotation axis. I.e., what it would take to do a single rotation of an object on all thre...

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Cannot input function handles into array
When you do this: basisN0 = @(x)[ 1 ]; basisN1 = @(x)[ 1, x ]; basisN2 = @(x)[ 1, x, x^2 ]; basisN3 = @(x)[ 1, x, x^2, x^3 ]...

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Analytically finding the roots of polynomials with symbolic variables
Tell the solve( ) function that the max degree of the polynomial is 3 to force explicit solutions for the result: syms a len p...

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Matlab unable to find solution to cubic polynomial
Tell the solve( ) function that the max degree of the polynomial is 3 to force explicit solutions for the result: syms a p = (...

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Replacing a for loop with matrix multiplication
result = sum(x.*(inv(SIG)*x)); or result = sum(x.*(SIG\x));

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How to find the numerical intersection points for a sine and linear function to find solutions ?
You can't do floating point calculations like this and expect the results to match exactly. You would need to use a tolerance t...

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