Community Profile # David Goodmanson

### David Goodmanson

Last seen: Today Active since 2012

#### Statistics

All
• • • • • • #### Content Feed

View by

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 ...

1 day 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 ...

4 days ago | 0

| accepted

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....

5 days ago | 0

| accepted

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...

6 days ago | 0

| accepted

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...

9 days 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 ...

9 days 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...

14 days ago | 1

| accepted

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]...

16 days ago | 0

| accepted

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...

26 days 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...

27 days 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...

27 days ago | 0

| accepted

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 ...

2 months ago | 0

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...

2 months ago | 0

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...

2 months ago | 0

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...

2 months ago | 0

| accepted

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 ...

2 months ago | 0

| accepted

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...

2 months ago | 0

| accepted

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...

2 months ago | 2

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 ...

3 months ago | 1

| accepted

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...

3 months ago | 0

| accepted

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...

3 months ago | 0

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...

3 months ago | 1

| accepted

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...

3 months ago | 1

| accepted

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...

3 months ago | 0

| accepted

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...

3 months ago | 0

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)

3 months ago | 0

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...

3 months ago | 0

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...

3 months ago | 0

| accepted