Community Profile # David Goodmanson

### David Goodmanson

Last seen: Today Active since 2012

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Computation of the bandwidth of a spectrum in wavelength domain
Hi Ikechi, the problem is basically that there are not enouch points to work with. lambda = lambdaaxis; lambda_range = (lambd...

ungefär 9 timmar ago | 0

How to calculate permutation powers
Hi lilly, Since the 1:n in the first row is just along for the ride, you don't have to carry it along in the calculation; you c...

2 dagar ago | 0

Does pwelch function adopt already the correction factor due to the window?
hello sy, At this point I believe that the documentation is misleading in that it appears to imply Power/unit_frequency but the...

5 dagar ago | 0

How do I define this integral function?
Hello LT, fun1 = @(x) x.^2 q1 = @(x) integral(fun1,0,4) q2 = integral(fun1,0,4) q1 = function_handle with value: ...

6 dagar ago | 0

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I am trying to solve for w using determinants
Hi Khaled, complex results do not seem right in this situation. M-M' ans = 0 0 0 0 % symmetric ...

11 dagar ago | 0

Help on trigonometric equation solution. Thanks a lot!
Hi Jack, Fortunately the solver is coming up with the correct angle, except for the 2*pi ambiguity. So, after the solver does ...

14 dagar ago | 0

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Calculation the integral of the exponential of a matrix
Hi raha, I think you can go with the following technique, which does integration, differentiation etc. at the eigenvalue level....

14 dagar ago | 0

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Problem understanding PCA and eigenvectors of covariance matrix
Hello Jaime, Scores are not the eigenvalues of the covariance matrix. Rather, 'latent' have that role. Scores are projections...

16 dagar ago | 0

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Lotka-Volterra, can you estimate steady-state values from just exploring a plot?
Hi Kamila, Here is one fairly simple way to find the parameters. The two equations are dhare/dt = k1*hare - k2*hare*lynx dl...

19 dagar ago | 0

How to solve a complicated equation?
Hi Cola, Since there is one equation and two unknowns, it must be possible to define, say, beta in terms of alpha, where alpha ...

19 dagar ago | 0

What is the difference between unwrap() function and principal value in finding the unwrapped phase?
Hi Ansam, The atan2 function does not unwrap anything. It merely produces a four-quadrant theta, with -pi < theta <= pi. Co...

24 dagar ago | 1

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Fast Fourier Transform Issue
Hi Anas, suppose you have N = 1000 points over an interval of one second. The time array is t = (0:999)/1000. [see note below]...

26 dagar ago | 0

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LOG PEARSON TYPE III distribution
Hi Raj, MODIFIED Since the pearson type iii is a gamma distribution with a shifted and scaled variable, that means you can use...

ungefär en månad ago | 0

real data FFT and reconstruction - frequency base issues
Hi Vmat. I believe that with 'rec' you may be confusing the time and frequency domains. The code below uses rec for the time d...

ungefär en månad ago | 0

How to Solve sytem of 7 equations with 6 unknown variables? How to combine any two equations? equations and variables given belowRequest for help
Hello Vijaya, This is an overdetermined set of linear equations of the form M*x = b and can be solved in the least squares sens...

ungefär en månad ago | 0

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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 ...

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

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...

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...

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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 ...

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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...

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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...

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 ...

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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...

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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...

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...

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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...

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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...

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