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David Goodmanson


David Goodmanson

551 total contributions since 2012

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Answered
Flatten Matrix in Row Major Order in Arbitrary Dimensions
Hello Lucas-Raphael, I'm not sure this is what you are looking for, but B = permute(A,[6 5 4 3 2 1]); % (however many dim...

3일 ago | 0

Answered
Looking for a function f(x,y,z) based on 3 points to calculate interpolated/extrapolated values with a linear relation
HI Appli, This is something Matlab does really well. I assume by 'linear relation' you mean that each point has a value c = a...

3일 ago | 1

| accepted

Answered
Cannot plot Fourier Transform
Hi Reza, If you take a look at X, the result is X = -((pi*w*sign(w))/2 + fourier(cos(4*t)/t^2, t, w)/2)/pi^2 which shows tha...

5일 ago | 0

Answered
IFFT integration doesn't match cumtrapz integration
Hi NIk, This is an Interesting problem. Let g be the function and G its integral. If you just want to key in on an improved r...

6일 ago | 0

Answered
Obtain eigenvalue from matrix and known eigenvector
Hi Henry, you can find the indices where x = 0 and cast those entries out of both x and the corresponding rows and columns of A...

8일 ago | 0

Answered
fftshift with even and odd number of data points (scaling the positive and negative frequency axis)
Hi Farooq, [1] For N odd, the frequencies before and after using fftshift (or ifftshift) are as you say: N = 9 example: fo...

15일 ago | 1

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Answered
Getting a smooth curve instead of two linear functions
Hi Arber, This can be done reasonably well by a hyperola whose asymptotes are the two lines in question. The hyperbola of cour...

28일 ago | 2

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Answered
eigs bug for 0 as lowest eigenvalue in parts of the matlab versions
Hi pl, 2018b does not list 'sa' as an option for eigs, so I am speculating that that 'sa' is legacy. However, compariing 'sa' t...

약 1달 ago | 0

Answered
Reduce the computional time to calculate the mutilplying two matrixes
Hi Thu, try % N = 1000; % M = 200; Q00 = reshape(Q0,N,N*M); ff = reshape(w'*Q00,N,M)'; This is approximately four times f...

약 1달 ago | 1

Answered
sine fit in matlab vs closed-form expressions (linear least squares)
Hi Thales, Before doing the least squares calculation it makes sense to try the less ambitious result of finding the right ampl...

약 1달 ago | 2

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Answered
Replace vector of idexes with values from another vector corresponding to those indexes
Hi Nate, c = b(a) gets it done. a becomes an index vector into the elements of b.

약 1달 ago | 1

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Answered
Division problems wiht matrix, calculation error
Hi Eduardo, It's quite likely that two of the displayed values for LineInf and LineSup are not what you think they are. The va...

약 1달 ago | 0

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Answered
Audio fft shape is too strange.
Hi eunbae, The code is pretty close. The fft of a real signal has positive and negative frequencies, and what you are seeing a...

약 1달 ago | 1

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Answered
Is It possible create a function that, given an equation, finds the value of the (x) so the two members are equal?
Hi Gianmarco, the two equations aren't coupled, and using fzero on Mp^2 seems to work. In the first equation I multiplied by b...

약 1달 ago | 0

Answered
Defining derivatives in ode45
Hello sina, If you turn the diagram around by 180 degrees and then let Ca <--> Cb, you get exactly the same diagram that you st...

약 1달 ago | 1

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Answered
3d Hemisphere transformation Problem from A to 90 degrees in Z axis to B direction
Hi Musa, In the figure you don't say which axis is which, but I will assume +x axis out of the page toward the viewer, +y axis ...

약 1달 ago | 1

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Answered
Binomial simulation decreasing error
Hello LD Using M in place of your i, the binornd(M,p*ones(1,N)) creates N draws from a particular binomial distribution. Thi...

약 2달 ago | 1

Answered
power of blackbody radiation
HI rabindra, The expression has a problem at the first point, lambda = 0. But I1 is so tiny near the origin that you can safel...

약 2달 ago | 0

Answered
Phase shift - different results with pi/2 and 1.570796326
Hi Buli, Although I don't have simulink, I think it is reasonably clear what is going on. I will assume here that -pi/2 is the...

2달 ago | 2

| accepted

Answered
to find the root of quantum transcendental equation
Hi pl, The boundary condition K*cot((KR) = -k (denoted by bc1 below) is for a wave function that is proportional to sin(KR) in ...

2달 ago | 0

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Answered
Solving inequalities without Symbolic Math Toolbox
Hi Andrik, I'm not sure why you are calling these equations 'inequalities', but if you are looking for a numerical solution to ...

2달 ago | 0

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Answered
Circularly exclude elements.
Hi Abhijit, try x = 1:n; x(mod([k-1 k+1]-1,n)+1) = []

2달 ago | 1

| accepted

Answered
1st element of the 'Amplitude' of a fft function
Hi NIma, As you point out, signal_FFT(1) is the sum of all the X values (or the mean if you divide by the number of points in X...

3달 ago | 1

| accepted

Answered
Select which legend entries to use depending on data set plotted
Hi Henry, A simple way to do this is, when a trace does not exist, substitute it with nan(1,n) or nan(n,1), keeping the array t...

3달 ago | 0

Answered
How to plot a numerical integral using the trapezoidal method
Hi Mahdi, I believe your units are correct, although dividing by D gives normalized conductivity and not absolute conductivity....

3달 ago | 0

Answered
FFT and IFFT: Random Phases
Hi Nycholas, Assuming signal is real and of length n, n even, then Y(1) is for frequency 0, the DC contribution, and it's real...

3달 ago | 1

Answered
Difference between x*(1e-n1) == x/(1en2)??
Hi Rob, The difference comes down to rounding of the very last digit in binary representation. It's interesting to use 'format...

3달 ago | 1

Answered
In the "ex_simrf_adc", there is a 50 Ohm connection with the voltage of 0.1 micro Volt input and it is converted to -142 dBm input and I am not able to get the exact power calculation. Could you please show me?
Hi Charles, I don't have simulink, but to convert from Vrms to dBm, dBm = 10*log10(Vrms.^2/50) + 30; Here Vrms.^2/50 is the p...

3달 ago | 0

Answered
problem of pdepe!
Hi Junyi, When you made the change, the flux went down by a factor of 1/pi^2. That's fine, but one of your boundary conditions...

3달 ago | 0

Answered
how do i plot sin(2pi*3t) * sin(2pi*15t)
Hi Jesus, what they are saying is % .* for element-by-element multiplication y=sin(2*pi*3*t).*sin(2*pi*15*t);

3달 ago | 0

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