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# David Goodmanson

### David Goodmanson

Last seen: Today Active since 2012

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energy signal
Hi k.v. For a given real signal y(n) of length N, n = 1 to N, the power at any point n is y(n)^2, the average power P is Pave ...

1 month ago | 0

How can I evaluate a complex definite integral?
Hi Valentin, It's not strictly necessary (see Paul's vpa solution) but it is advantageous to scale things properly before doing...

2 months ago | 0

How to use sinc function
Hi Ricardo, while it might be nice to have the Signal Processing toolbox, you certainly don't need to buy any toolboxes to do t...

2 months ago | 0

how to find concave angle between three points
Hi Eliska, One thing that does not seem to be mentioned so far is your use of the norm function on the determinant. That makes...

2 months ago | 0

calculation error in hyperbolic function
one possibility: (tanh(-10))^2 ans = 1.0000 % correct although tanh(-(10)^2) % traveling parenthesis ans =...

2 months ago | 0

Partial derivative with respect to x^2
Hi Yadavindu, df/d(x^2) = (df/dx) / (d(x^2)/dx) = (df/dx) / (2*x) which you can code up without the issue you are seeing.

3 months ago | 1

Solving a system of Non-linear Equations with Complex numbers
Hellol Aravindhan, not solved by Matlab, but a bit of algebra shows that with x(1) = 2000*a x(2) = 2000*b x(3) = theta/5 t...

3 months ago | 0

Increasing the caclulation speed while using loops
Hi Hamid, Hi Hamid, I have not speed checked this but it should be faster (the range in your example is different from the draw...

3 months ago | 2

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How to introduce a phase shift to a existing vector
I assume that you are given the oscillatory function V in an array, with no accompanying array for the independent variable to s...

3 months ago | 0

Average of random variables from two Poisson distributions?
Hi Jonne, I assume you want to look at the distribution for a period of one minute, whenever that might occur. As opposed to l...

3 months ago | 1

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How to extrapolate a plot?
What is being fitted is T vs. C, with the idea of extrapolating to T=0. The C variable, C=log((A0-A1)./(A-A1)) contains A, wh...

3 months ago | 0

z transfer function evaluates to inaccurate value near z=1
Hi Ashish, This function, ((1-1/z^2)/(1-1/z))^6 is identically equal to ((z+1)/z)^6 so you can just use that. And it does ...

3 months ago | 0

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Why am I getting wrong spectrum applying FFT comparing with correct spectrum?
Hi Jiang, There are a couple of things going on here. The expression for FFT is not correct. Since you are taking the real pa...

3 months ago | 0

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Solve system of equations with some knowns and unknowns in the same matrix
Hi Yusuf, I'm later on an answer (and losing the race more often, to the extent that there is a race, which to be honest there ...

3 months ago | 0

How can I code a contour integral representation of cosine?
Hi Richard, this integral converges very slowly along the vertical path gamma-i*inf to gamma+i*inf. Convergence depends on wha...

3 months ago | 1

reverse lookup table from vector multiplikation with unknown vectors
Hello Henning, Assuming that you want column vectors a and b such that their outer product C = a*b' is as close as possible to ...

4 months ago | 1

How to define color on matrix figure
Hi Jan, the following method comes up with black not just for values that are exactly zero (I don't know how likely that might ...

4 months ago | 0

Question using IFFT, try to transform continuous 1 from frequency in time domain
Hi Jan, In the secnd example the dirac value should be quite large, In fact it should be 3e5, the number of points, not half o...

4 months ago | 0

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fminsearch for a function f(x,y) = x^4 -3xy+2y^2
Hi Ibraheem, While it's useful to find out about how to get fminsearch to cooperate, that's hardly necessary here. For the min...

4 months ago | 0

Random numbers generation problem
Hi Daniel, here is one way, basically the sieve of Eratosthenes. nmax = 1000; a = randi(nmax,1,1e6); a(rem(a,2)== 0) = []; ...

4 months ago | 0

different result of PCA function and my PCA
Hi Farshad, Each column vector in the cof matrix is arbitrary up to an overall constant of absolute value 1, which for the case...

4 months ago | 0

My code is outputting very illogical answers for the second block (my second vector loop equation).
Hi Emily, No one seems to have mentioned that there are two independent solutions for the angle pair angle3 and angle4, since i...

4 months ago | 0

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My code is outputting very illogical answers for the second block (my second vector loop equation).
Hi Emily, If VLE1 and VLE2 are lined up typographically, you have VLE1 = @(x0) [(R2.*cos(theta2_all(i)) + R3.*cos(x0(1)) -...

4 months ago | 0

xcorr and finddelay giving erroneous results for offset sine waves
Hi James, This effect is due to a peculiarity in finding delays when your sample is cut off sharply at each end. The following...

4 months ago | 1

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Would you tell me the code for Fisher Pearson skewness?
Hi Chris, y = rand(1,100); % some data m = mean(y); n = numel(y); scalc = (sum((y-m).^3)/n)/var(y,1)^(3/2) s = skewness...

5 months ago | 0

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Why doesn't the kurtosis function work properly for complex numbers?
Hi Guillem, Both the standard deviation and the variance (std and var) work correctly for complex argument, so kurtosis appears...

5 months ago | 1

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SIR model with recovered individuals may lose their immunity and become reinfected with the disease. But came with a failure about integration tolerances
Hi Julian, I have doubts about the equations, because with dq(1) = -S as you have, the equations are equivalent to S = -beta*S...

5 months ago | 0

what does the positive and negative values concave mean?.
Hello Aisha, You are looking at a polynomial function of z, with two roots as you stated. To see what is going on, it helps to...

5 months ago | 0

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