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# David Goodmanson

### David Goodmanson

902 total contributions since 2012

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Answered
Fitting impedance of simple randles circuit to Fourier transform formula
Hi F^2 I believe you are trying to fit an incorrect magnitude, which can of course lead to nonsense. The correct expression is...

9 hours ago | 0

Answered
Want to Get Plot To Have Contunuous Angles, Not Stay between -180 and +180 Degrees
Hi Jon, use unwrap(your_data,180) where 180 is just an example and can be anything smaller than the size of the jumps (but no...

4 days ago | 1

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Answered
Issue with getting correct FFT phase plot
Hello SB, the issue here is that the signal window is not the correct width to give the periodicity that you would like. Right...

4 days ago | 0

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Answered
Permutations of ordered set where only one object changes its position.
Hi Michael, no there is not. CBA is a permutation, and it cannot be made to fit the pattern.

5 days ago | 0

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ode23, ode45 acting weird - why?
Hi William, Very interesting behavior. Different look but still impressive when the span ends at 40.1. I think the reason may...

5 days ago | 1

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Answered
Equation for Fourier Series
Hi Romain, increasing the nomber of points is a good idea. I used t=0:0.01*10^(-6):6*10^(-6); but I believe there is also a ...

9 days ago | 2

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Answered
Symbolic solution by matching coefficients in trigonometric equation
Hello Gabriel, here is one way syms id iq x1 y1 th1 th2 eq1 = id*cos(th1) - iq*sin(th1) == 2*x1*cos(th1) - 2*y1*sin(th1) eq2...

13 days ago | 0

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optimization using lagrange multipliers
Hi Lal, The problem is that you have V(x,y,z) = x*y*z as a function, but you do not define a fixed value for the volume. The ...

16 days ago | 1

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Answered
Problem in performing IFFT
Hi Susmita, A couple of things going on here. First, it's good to use more points. Use a lot more points. There is no need t...

20 days ago | 0

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Answered
Obtaining the envelope of AM signal using hilbert transform
Hi Bernardo, I don't think there is much doubt that the effect is due to a DC offset in the signal. In your figure, both the r...

25 days ago | 2

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Inserting new element after each element of an array
Hi Neeraj, not having the communications toolbox I used dec2bin instead, which gives a character array but it is basically the ...

26 days ago | 0

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Difference of amplitude after FFT calculation
Hi SO, The y array consists of (supposedly) just one frequency, but aside from the scaling your plot shows spread-out frequency...

26 days ago | 0

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Answered
Natural Cubic Spline interpolation
Hi Bella, you can get the coefficients of the piecewise polynomials for each segment with pp = interp1(x,y,'spline','pp') or ...

1 month ago | 0

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solving simultaneous equations of fourth order PDE in MATLAB
Hello Devansh Since you have boundary conditions at both x=0 and x=L you can use bvp4c to solve this. But I believe you have t...

1 month ago | 0

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the final result of laplace transform still contain laplace function?
Hello ZH Matlab doesn't know if taoc is positive or negative. If taoc is negative, the calculation can't really be done. Tha...

1 month ago | 1

Answered
Help With ODEs Solver(ode45)
Hi Ahmed, repeating the plot command every time in the nested for loops is not helping, For a smaller case (I didn't want to w...

1 month ago | 1

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Answered
Symbolic differentiation of Bessel functions is incorrect
Hi Sam, There is really nothing going on. Both of those identities are correct, as you can check numerically. There are sever...

1 month ago | 0

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Answered
Permutation matrix P in the qr function
Hello Gabriele, I don't think you can conclude anything about the columns of A. That's because the usual qr decomposition is u...

1 month ago | 0

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Answered
Antenna radiation pattern rotation
Hi Marina, Since you are using surf, I am going to assume that you have three matrices x,y,z, each of size m x n, appropriate t...

1 month ago | 1

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Answered
How to create an average of 2 lines on a single graph
Hi Charley since the second half of the distance array has exactly the same values as the first half (only reversed), you can u...

1 month ago | 0

Answered
Euler Angles from Rotation Matrix
Hi Gregory, If you mean you want the form of the rotation martrix in terms of alpha,beta,gamma, that's just syms a b g R1 = [...

1 month ago | 1

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Answered
roots of the complex equation with one variables
Hello Varun, Your code gives for solutions b = 30.857 - 175.74i -94.032 - 211.56i 70.398 - 342.7...

1 month ago | 0

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multiple r values for multiple theta values
Hi Allan For an element-by-element calculation, use ./ and .* rather than / and * theta=[pi,3,2.8,2.5,2,pi/2,1.3,1.0,0.75...

1 month ago | 1

Answered
Modifying 'Bessel second-order ordinary differential equation' in matlab library.
Hi K^2, Picking kr as the argument, take a look at J(kr) and do the differentiations on d^2/dr^2 J(kr) + (1/r) d/dr(J(kr). Ta...

2 months ago | 0

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Answered
solving a system of 2nd order 2 ODE: output vector length not matching the initial condition vector length
Hi yosri, the reason this is happening is that the expression for dy/dt has four elements, but one of them contains diff(y(4)) ...

2 months ago | 0

Answered
Create a vector field
Hi ALvaro, The code below sets P=Q=0 to make the spacial dependence more clear. Rather than meshgridding the 1d velocity vecto...

2 months ago | 0

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Answered
how can i calculate z^2 distibution?
Hello JS By gaussian I assume you mean the normal distribution, mean 0, std deviation 'a' f(z) = N*exp(-(z/a)^2/2) with N =...

2 months ago | 0

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Answered
Solve function returns expression in terms of z
Hello Ashmika, You do have a symbolic solution for h, which goes to show that symbolic solutions are not always the ideal. The...

2 months ago | 0

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Answered
How can I get randperm to return a permutation of a vector that has no entries at their original positions?
Hi Darcy, the methods I have seen here seem to involve trying randperm and rejecting the result if an element remains in the sa...

2 months ago | 0

Answered
Imaginary numbers when solving ode (ode15s)
Hello YF, whenever unexpected complex quantities start appearing, it's time to look for the usual suspects, which tend to be ei...

2 months ago | 0

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