David Goodmanson

Last seen: 1 day ago

David Goodmanson

920 total contributions since 2012

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Answered
Running out of memory selecting parts of a large sparse matrix
Hi Benjamin, I believe this works as required. This example is 4e5 x 4e5, with 99.99% zeros. On my pc it takes 3 sec to make ...

18 days ago | 0

Answered
How can integrate and differentiate spherical Bessel functions in Matlab
Hello MB, [1] Dimensionally, k can't be wavelength. Maybe you meant the wave number, 2pi / lambda. [2] The integrand increas...

19 days ago | 0

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Zeros and ones vector
Hi Fieke, My previous effort answered the wrong question (the code for that is under the dashed line below). You want a matrix...

25 days ago | 0

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How to produce frequency vector corresponding to FFT() samples?
Hi Samuel, In the code you borrowed, t is just a time array so that you can create a function of time. The t array starts at 0...

27 days ago | 0

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Amplitude of FFT is not correct
Hi Meikel, You are multiplying your signal times a window, which reduces the signal amplitude. That has to have a significant ...

27 days ago | 0

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Inverse fourier transform is not regenerating original signal amplitudes
Hi Sebastian, You appear to be treating fs in somewhat casual fashion. If fs = 1e5, then for a 1 sec pulse duration the number...

1 month ago | 0

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How to vectorize the following code for matrix insertion?
Hi Jordan, Here is one method. Whether or not it is faster than the for loop method is another question. The code does exactl...

1 month ago | 2

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How to obtain the exact value of wavelength from a 2D FFT amplitude vs wavenumber plot like it is obtainable from 1D FFT amplitude vs wavenumber plot?
Hello SB, I am speculating that the issue is the offset from the correct frequencies in the fequency domain plot. The culprit ...

1 month ago | 1

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Answered
Why is the radiation pattern does not show the required steering angle?
Hi ZW, In the code below, the key line is s = s + exp((-1j*k*d*(i-1).*sin(angle_1rad(th))) +1j*AF(i)); %equation for field w...

1 month ago | 0

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Answered
Why do these two codes give different covariance matrices?
Hi Sadiq, cov subtracts mean from each column of S, and also divides by (size(S,1) -1). Also S and S' have to be multiplied in...

1 month ago | 0

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Mean of the rand function goes against theory
Hi Tarek, the reason that you don't see 0.5 is that you are taking a finite number of samples, 1024, from the distribution. Du...

1 month ago | 1

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Answered
How can I find an orthogonal vector?
Hello Sue, use null of the transpose of p: syms a p=[1;-a;0] n = null(p.') n = [ a, 0] [ 1, 0] [ 0, 1] and each col...

1 month ago | 1

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Answered
Generation of a basis vector following a constraint.
Hi Vira, The for loops that you did are a good approach, but like you say this will become impractical as the length of the vec...

1 month ago | 0

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Answered
Output of Deconv function Matlab
Hi Aleem, [1 -4] does not divide evenly into [1 -3 -52] so there is a remainder: [a b] = deconv([1 -3 -52],[1 -4]) % b is t...

1 month ago | 0

Answered
how to create new cumulative frequency array from two existing arrays
Hi BW, mu = 50 sigma = 10 Y = normrnd(mu, sigma, 1,1000); v = linspace(1,1000, 1000); a = cumsum(Y<=v)

2 months ago | 0

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Ode45 with 3 non-linear equations
Hi Ahmed, it might be a good idea to go back to the original derivation for this system. Instead of that, you can rewrite this...

2 months ago | 0

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High Resolution fft2 image
The nested for loops use the same variable i, meaning that the outer one doesn't do anything except run through the inner one fi...

2 months ago | 0

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How can i solve the Error using erfc- Input must be real and full
Hello Siti, Although erfc does not take complex arguments as you know, the kummer U function is available and does take complex...

2 months ago | 1

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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...

2 months ago | 0

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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...

2 months 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...

2 months 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.

2 months ago | 0

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Answered
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...

2 months 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 ...

2 months 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...

2 months 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 ...

2 months 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...

2 months 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...

3 months ago | 2

Answered
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 ...

3 months ago | 0

Answered
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...

3 months ago | 0

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