David Goodmanson

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David Goodmanson

778 total contributions since 2012

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Answered
Strange behaviour computing l1 norm of rows of a matrix
Hi Christoph, It appears that something has gone wrong with keeping track of sparse nonzeros in the last row. However, if the ...

3 hours ago | 0

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About FFT of cosine function
Hi mk, In order to get just the two sharp peaks you need to have exactly n oscillations in the time domain. Otherwise the wave...

5 days ago | 0

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impulse response for difference equation
Hi Roger, try bb(N+1) = -power(a,N); which is what you actually have. I think you'll lilke the resulting plot.

12 days ago | 0

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How can I solve this set of complex equations?
Hi Stefanos, As has already been mentioned, the 4th equation is just the definition of V0' and is independent of the first thre...

13 days ago | 0

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Changing a parameter in a differential equation?
Hi Sean, you can pass the value of epsilon into the ode function with [tSol,YSol]=ode45(@(t,Y) quantumsystem(t,Y,epsilon),tRan...

16 days ago | 0

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Regularized hypergeometric function 1F2 within matlab?
Hi Wozciech, if you add a prod function, part3 = prod(gamma([(1-n/2),(3/2 - n/2)])) then you're good to go. Or, you could us...

18 days ago | 1

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Matrix multiplied by inverse is not giving correct answer
Matlab is telling you the answer, that the matrix (call it M) is close to singular or badly scaled (singular in this case). M h...

18 days ago | 1

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Complex number and fft
Hi Nmak, you are just getting into standard numerical precision issues. The fft and ifft involove complex variable calculation...

19 days ago | 1

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Interpolating and resampling around closed curve to calculate centroid
Hi Sofia, Since your points are pretty closely spaced, there is not much need to interpolate the points. The method below pick...

19 days ago | 1

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Regularizied hypergeometric function gives an error for z being greater than 1.
Hi Wojciech, I am assuming that there is no problem when n is not an integer, only when n is a positive integer greater than 1....

21 days ago | 1

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Smooth derivative of a matrix
Hi Daniel As you know, multiplying each column of a unitary matrix by a scalar phase factor still results in a unitary matrix (...

26 days ago | 1

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solve and plot nonlinear system of equations with no explicit solution
HI Cengizhan, MODIFIED The first equation above is (-1/2)*(cos(x)*cos(z)+sin(theta)/psi) = 0 (1) which has an extraneous ...

28 days ago | 0

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Check whether the symbolic eigen value of a matrix is positive or negative
Hello TS with your definition of Am we have simplify(trace(Am)) ans = -(672*d*g + a*d^4 + 36*a*g^2 + 576*g^2 + 42*a*d*g + ...

29 days ago | 1

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Large integer rounding problem
Hello HS, you ran into the limits of double precision numbers. However, (1+x/n)^n = e^x*f % f = correction factor...

30 days ago | 0

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Remove peak at 0 hz of fft
Hi Emmy It's all in how you view things. Literally. Here is what happens when using x - mean(x). fs = 1000; N = 30000; fig...

1 month ago | 0

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Using 'solve' on a vector of line equations?
Hi Jonathan, It's not totally clear if the geometry is such that there is a separate t value for each row of the hits{1} and hi...

1 month ago | 1

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Calculating the contributing terms of a summation equation
Hi Bharath, suppose the sum involving q is done over a dummy index j instead of i. It appears that Y and y are vectors of the ...

1 month ago | 0

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use the previous result of a function in the calculation
Hi Matthew, there is definitely a better way. Y = filter(B,[1 -A],X) Here the assumption is that X is an input vector and B i...

1 month ago | 0

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Plotting Fourier series from fft output / how to obtain fundamental freq.
Hi Morgan, In this situation with periodic waves, the ftt is divided by L, as you have. The fft is at heart an operation using...

2 months ago | 0

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quintuple summation using a for loop
Hello Wyatt, The sum comes out zero because it is, in fact, zero. Each term in the desired sum is ((-1)^(iw+jw+k+l+p+q))*con...

2 months ago | 0

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PSD from Wiener Khintchine and FFT
Hi Jan-Niklas It's easier done with convolution instead of correlatation, so convolution is first here. fft does circular conv...

2 months ago | 0

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Why the coordinate doesn't make sense after rotation matrix (rotx)?
Hi Jiali, from your results it looks like you are using the usual form of the rotation matrices, function M = Rx(theta) % an...

2 months ago | 0

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differential equation with mixed linear and log derivatives - proper setting
Hi Patrezio, d(log(x)) = dx/x, and you can insert that result in three locations to obtain eq1 = x*diff( log(y), x) + x*diff( ...

2 months ago | 1

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Are there any built-in way to calculate inversions?
Hi Ivor, I do not know of one, but here is one way to accomplish it p = [3 6 1 4 5 2]; % for example inversions = 0; for...

2 months ago | 0

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convolution with gaussian kernel using fft
Hi LM The code below takes your approach but modifies some of the details. [1] The array sizes are odd x odd since you get th...

2 months ago | 1

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I have 744 hourly wind data points for the month of january i.e 24 data points for each day (744 for 31 days) For each day I need to fit the 24 hourly data points with the non linear function C(1)+C(2).*sin(2*pi/24.*(x-C(3)))+C(4).*sin(2*pi/12.*(x-
Hi Gourav, this is not really a nonlinear problem. That's because dropping some parenthesis) C2*sin(2*pi/24*(x-C3)) = -C2*[ s...

2 months ago | 0

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How could I find the maximum closed contour line?
Hello YC, Since a saddle point is where the contour lines go from closed to open, the idea is to find the location of the saddl...

2 months ago | 0

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Normalization of FFT output
Hello Vittorio, In the gaussian case, the waveform has died down to zero each end (technically it's not zero, but it is smaller...

2 months ago | 0

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Error in a function
Hi Morne' Here Matlab assumed that the call to the function was part of the function itself. In a script, functions must be lo...

2 months ago | 0

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FFT: scaling for correct amplitude
Hi Eric, It's not the specific details of the signal so much as it is the context. If you are transforming what is basically a...

2 months ago | 1