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David Goodmanson


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David Goodmanson

761 total contributions since 2012

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Answered
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 day 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...

6 days 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...

10 days 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...

14 days 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...

15 days ago | 0

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Answered
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( ...

16 days ago | 1

Answered
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...

17 days ago | 0

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Answered
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...

19 days ago | 1

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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...

20 days 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...

22 days 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...

22 days 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...

23 days ago | 1

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Different eigenvectors when using eig and null functions
Hi Mohammed, I tossed in some 'double' functions to make the comparison easier A = [3 2 ; 7 -1]; syms x; a2a = sym(A); pol...

25 days ago | 1

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Answered
Time axis explanation required
Hi Saad, 'time' is (almost) the total length of the time record, so it will not be the spacing when setting up the time array. ...

26 days ago | 0

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Analizing the charges and discharges of a capacitor conected to a square wave voltage source
Hello Virginia, As you progress along the square wave, each time you get to a new half cycle there is of course a new applied v...

27 days ago | 0

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Answered
How to solve a set of coupled odes that depend on derivatives
HI charlie, dx4' depends on dx2' and dx3' explicitly. But since dOmega_e_dz and dV_e_dz are also in the expression for dx4', d...

29 days ago | 0

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Issue with gammainc(x,a) for small x and larger a
Hi John, Matlab does not appear to have a symbolics version of the incomplete gamma function, but it's still possible to make p...

1 month ago | 0

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im using 'dsolve' for 2nd ode with dirac function but matlab returns 1/2 of constant
Hi Song-Ha Your statement " the answer should be [constant] *exp(-0.4607 * t) * sin(3.0003*t) " is missing a very important f...

1 month ago | 0

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Hypergeometric Function in Matlab
Hello PM, The variable l does not come out so well in this font so I'll call it q instead. SInce both -q and -n are negative, ...

1 month ago | 0

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Answered
ODE45 Code Application
Hi James, [t,U] = ode45(@Velocity, [0, 20], .001); plot(t,U) function Udot = Velocity(t,U) M = 100/6*pi*0.04^3; g=9.8; A...

1 month ago | 1

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Answered
How to simplify a symbolic equation, but still keep the denominator
Hi LZ syms x y a b eqn1 = b*(x/a + 1) == b*y/a; % This is the equation, I would like to cancel "b" at both side, and still kee...

1 month ago | 1

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Answered
Eliminating and counting rows that contain a pattern that already appeared
Hello Spencer, I assume that the patterns you mean have a length of 5. The way that you have set the the problem, 44313 (B row...

1 month ago | 0

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Answered
Fast Fourier Transform component detection issue
Hello awezmm, This occurs because of a combination of aliasing and the spacing of the chosen frequencies. For sampling frequen...

1 month ago | 1

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My code won't run, related to ode function
Hi Dardenella, try the same thing only with [t,Y] = ode45(@(t,Y) f(t,Y,omega0,p), [0,10],[y0,v0]); % solve for 0<t<10 [n...

1 month ago | 0

Answered
How to make specific elements in a 3D matrix zero?
Hi Rabia, try for yy=1:10 temp = Costyearlydata(:,:,yy); temp(D(:,1,yy)) = 0; cost1(:,:,yy) = temp; end

1 month ago | 0

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Answered
constructing a difficult large matrix
Hi ektor, I presume you are interested not so much in the in the matrix A as in the 1000 scalars you get after you multiply eac...

1 month ago | 0

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Answered
Plot the travel for an electron by using ode45 (involving matrices)
Hi Ibrahim, There is nothing wrong with using matrices in this situation, and the plot is fine, insofar as it is plotting what ...

1 month ago | 1

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Answered
Solver Equation not giving solution
Hi Diogo, Matlab syms can solve this, but it needs some help, which is squaring both sides of eqn3 to form a new eqn3. Also si...

1 month ago | 0

Answered
Mutual Inductance ODEs and wireless power transfer
Hello Tucker, You have two first order DE's so there is no need to have a vector x with four components. Four is appropriate f...

1 month ago | 0

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