David Goodmanson

609 total contributions since 2012

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Answered
Implementing a sum with summands of unequal spacing inside an integral
Hi Richard, I don't claim to be a professional although I did use Matlab at work, and here is how I would do this. The main th...

2 dagar ago | 1

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Does the permute function have a bug?
Hello ZY, see 'help permute'. Permute puts the dimensions in the order listed, so in this case the old 4th dimension goes firs...

2 dagar ago | 0

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Is it possible to create periodic boundary conditions for a matrix with linear indexing?
Hi Tom, mod(k,N)+1 for the raised index, k+1 mod(k-2,N)+1 for the lowered index, k-1 and these do give the correct vector of ...

5 dagar ago | 0

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Answered
how to solve the equation: xdot=AX+Bu; where u=sin(2t)
Hi Ebraheem, ode45 is fine with explicit time dependence in the calculation of xdot: [t, x] = ode45(@smc5,[0, 10],[1, -2]) pl...

5 dagar ago | 2

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Answered
Series expansion with Legendre polynomials
HI James, I won't address how one might print the result, but the mistake in the algrbra is that you should use y(i) = ((2*i+1...

5 dagar ago | 0

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Chua Oszillator in Matlab, Chaos
Hi Albin, In your second version, the equation for xdot is dimensionally incorrect. Changing it to xdot = (1/C1)*(G*(y-x-g));...

6 dagar ago | 0

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Meshing a complex function with limits
Hello Haider, for someone who is new to Matlab you are doing well. You just need a couple of changes. First, you forgot that r...

9 dagar ago | 1

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plot Gibbs phenomenon individually???
Hi Neptune, I agree that my comment on what the Gibbs phenomenon actually is was not very helpful to the actual problem at hand...

11 dagar ago | 0

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Automatic Complex Conjugate in ftt
Hello Ha Oe the quote command is not just the transpose, it's the complex conjugate transpose (Hermetian conjugate). For the s...

11 dagar ago | 1

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Answered
The input signal is complex conjugate, but the IFFT output is complex!
Hello yz, The problem is that to produce a real ifft, the first element of Ax, which is the f=0 term, has to be real since that...

11 dagar ago | 1

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Answered
Why is dsolve returning an arbitrary constant?
Hi David, you need slightly different syntax. syms y(t) g L c Dy = diff(y) S = dsolve(diff(diff(y(t))) -L*y - g == 0, y(0) =...

12 dagar ago | 0

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Answered
How to plot a maximum value on an existing line graph
Hi Grace, Here is an example of what I think you are looking for. The idea is to use the second output of max to find the inde...

12 dagar ago | 0

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Matlab output is not matching with the mathematics...
Hi Hari, the problem is that 2*pi*f*t is a nice linear function of t for all t, but the output of acos is restricted to the ran...

12 dagar ago | 1

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Answered
Non Linear DE solving using ODE45
Hi Muhammad, with that set of constants, the time has not been run out far enough to see the final result. Try changing the ti...

12 dagar ago | 0

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Answered
ODE45 calculating the total energy in the system and checking the solver
Hi Kostas, The problem is in the calculation of the dissipated energy which is not any kind of sum of (y C dy/dt), but rather t...

12 dagar ago | 0

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Answered
Constructing an FFT-like result array.
HI betz, All of the following applies if the time domain waveform is REAL For a N point fft, N even: (a) point 1 is the four...

22 dagar ago | 1

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Answered
Equation of Motion is Blowing Up
HI Samuel, I won't have access to Matlab for a few days so this needs to be verified, but I believe that in the last line of th...

26 dagar ago | 0

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transfer functions arithmetic - is it distributive?
Hi Kapil, The second expression is merely the first expression multiplied by (z-1)/(z-1). So the two are equivalent, with the s...

26 dagar ago | 0

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How can I re-write an anonymous function into a standard function?
Hi Jesus, [ CORRECTED to include a minus sign ] function [returns,variance] = MultiObjective(mu,C,w) returns = -mu'*w'; ...

27 dagar ago | 0

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Answered
I'm trying to ad a condition to an equation
Hi Xavier, I don't think your original function is overcomplicated at all. It's straightforward code that is self-commenting, ...

29 dagar ago | 1

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Cholesky Decomposition Column-Wise Algorithm Implementation
Hi J, I added to the code in your last comment by including the obvious missing 'for' statements, etc. After that, it's pretty...

2 månader ago | 1

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scientific notation in each element
Hi c^2, try "format short g" beforehand. Things stay that way until further notice. To go back to the default you can use ...

2 månader ago | 0

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FFT of ON OFF signal
Hi imran, you appear to be pretty close on this. The code below uses ftshift to put f = 0 at the middle of the freq array, and...

3 månader ago | 0

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Centered FFT & DFT: cannot devise required phase shift vector(s).
Hi Peter, here are some phase shifts. I shortened up some of the variable names to make it easier (for me, anyway) to follow w...

3 månader ago | 1

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Answered
Why is 1/ones(3,1) OK while 1/ones(1,3) is not OK?
Hi Yuki, In the expression x = 1/ones(3,1) multiplying both sides on the right by ones(3,1) gives x*ones(3,1) = 1. The row ve...

3 månader ago | 2

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Answered
Bivariate Normal Distribution different for expression and mvnpdf()
Hello Aishwarya, The problem here is that the array x is 2x31 and does not have every possible combination of an element of X1 ...

3 månader ago | 2

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Answered
How do you find the approximate interval that displays the solution?
Hello Isabel, I believe the idea here is that when lambda is large enough, the expression for Tb gets increasingly close to Tb_...

3 månader ago | 0

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ODE45 to solve a system of two coupled 2nd order ODEs
Hi Ricardo, I am inferring that you have the following system with fixed points S: S---k1---M---k2---M---k1---S Then eqn 1 is...

3 månader ago | 0

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Answered
How to element wise exponential of a matrix
Hi Titas, dy = Columns 1 through 10 15.7800 31.5600 47.3400 63.1200 78.9000 94.6800 110.4600 126.2400 142.0200...

3 månader ago | 1

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Answered
Anttena Paterns radiation patterns
Hello MT, The basic issue is setting phi_3db to degrees, but there may also be a problem with the basic definition of phi_3db (...

3 månader ago | 0

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