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David Goodmanson


David Goodmanson

533 total contributions since 2012

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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...

6 days ago | 0

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 ...

8 days 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 ...

12 days 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) = []

13 days ago | 1

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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...

18 days ago | 1

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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...

27 days ago | 0

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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....

27 days ago | 0

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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...

1 month ago | 0

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...

1 month 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...

1 month 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...

1 month 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);

1 month ago | 0

Answered
My matlab plot is blank when I plot
Hi Henry, In the definition of H1, use ./ instead of / so you get term-by-term division. To spot the error, one straighforwa...

1 month ago | 1

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Answered
Determine the maxima and minima of the function
Hi Maria, for a fumction f(x), fminbnd determines the value of x where the minimum occurs. You would have found p09xmax if you...

1 month ago | 0

Answered
Using find between two points
Hi Darpan, try it with just one & sign. && is for scalar comparisons, and you have a vector on each side.

1 month ago | 1

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Answered
Help to approximate this integral...
Hi M^2, I am assuming that y(t) is strictly monotonic increasing or decreasing so that the inverse exists. It's good if the y ...

2 months ago | 0

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Why pca on my matrix gives the first number in latent matrix greater than one?
Hi Penny, Is there a reason that you think that a matrix of all ones and zeros can't have a latent value greater than 1? Here ...

2 months ago | 1

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Answered
Finding miminum and maximum of function f(x)
Hi Faris, In 1d I assume you had y = f(x) with an x vector of length n, so its index is 1:n. Then [ymax ind] = max(y) xmax =...

2 months ago | 1

Answered
Polynomial in S domain shows zero values
Hi Dushan, this is merely a display issue because L*C and R*C are so small compared to 1. Try the same thing with format shor...

2 months ago | 0

Answered
Unable to find explicit solution to differential eq
Hi Ditlev, I believe this does have an analytic solution that is not overly complicated, of the form x = (a+be^(-ct)) / (f+ge^...

2 months ago | 0

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Answered
fftn, fftshift and interp3
Hi David, I believe the reason for this is the following. Staying in 1d for simplicity and not worrying about constants, the f...

2 months ago | 0

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Answered
Using matlab to evolute a simple vector , but not fit the inference
Hi Darcy, It appears that the rule you want is a(t+1,i-1) = a(t+1,i-1) + 1 which does give the result you are looking for. ...

2 months ago | 0

Answered
How to determine the rotation matrix for rotating one vector to align with another ?
Hi Tao Feng. One candidate is products of rotation matrices about x,y and z, basically Euler angles. Including traditional Eul...

2 months ago | 0

Answered
Trapezoidal Estimator for the integral
Hi Furkan, case 1: you are calculating Area2 with the trapezoidal approximation, but comparing it to Area1_actual when computi...

2 months ago | 1

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Answered
How to determine time-domain amplitude from frequency domain
Hi pimovietc, I'm not sure what is going on with the use of fs in some of your expressions so I will use a different but simila...

2 months ago | 1

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Answered
conv not giving the expected results. Why?
Hello Tara, You want to approximate an integral by using a sum. In general, for equally spaced t values with spacing deltat, t...

2 months ago | 1

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Answered
How can I plot a linear regression line on a loglog scatter plot in MATLAB?
Hi Samaneh, I will abbreviate moment and average_slip as x and y here. Since log log space is evidently the most meaningful re...

2 months ago | 0

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Answered
Matlab taking a very long time to give output when my error limit is low
Hi Anthony, The reason for this is that one of the initial boundaries, say the lower one, never gets changed while the upper bo...

2 months ago | 0

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Answered
Why do I get repeated values for a variable when its parameters change with every iteration?
Hi Michael, Vave(j,k) and Ptube(j,k) are assigned values that depend on row index j but not column index k, so each row conta...

2 months ago | 0

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Answered
FFT of Large CSV File - Fundamental doesn't match data or simple sine test case
Hi Calvin, this is yet another example of the destructive power of using nextpow2 with the fft in the wrong circumstances. I t...

2 months ago | 0

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