David Goodmanson

Last seen: 1 day ago | Active since 2012

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Why is the magnitude spectrum spreaded over certain frequency range instead of line spectrum in FFT?
Hi lekhani, The spread is happening because you don't have a pure, CW, constant-amplitude cosine wave in the time domain. That...

12 days ago | 0

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Answered
How to determine the lag angle between two snine wave
Hi Hassan Consider the complex wave exp(i*(w*t+theta)) = cos(w*t+theta) + i*sin(w*t+theta) While it's true that the cos a...

12 days ago | 0

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Yellow Colormap on contour lines
Hello Juan using: doc colormap will bring up all of the preconstructed choices. In this case it looks like 'hot' was used. 'a...

12 days ago | 0

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I am trying to find values of four constants from four equations. Yet the code is unable to give out values
Hi Sahir, you have to load this beam in some manner in order to get nonzero deflection. If all the boundary conditions are set...

13 days ago | 0

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What is this fft code doing?
Hi kcee, The code (I'll refer to it by line below) is not doing what it is doing very well. Let's start with the good part, th...

16 days ago | 0

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How to approximate a triple integral over a rotated grid?
Hi Oscar, Before the cyinder is tilted, you are describing the volume with cylindrical coordinates and finding the moment of in...

17 days ago | 0

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How to plot the subplots but with less lines of code?
HI muhammed all you need to do is put the subplots into a for loop and change the things that vary with subplot. That is the d...

18 days ago | 1

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Answered
I have code which calculates the electric potential due a single charge. The results are concentric circles (Correct results) but don't match the theoretical data
Hi Matthew, probably a bit late to be answering this now, but thanks to some editing done by John Kelly at Mathworks it provide...

19 days ago | 0

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Huffman Dictionary, error with index exceed when i give specific probabilities.
Hi Rafael, sum(probabilities) ans = 1.0003 SInce the probabilities don't add up to 1, the code is going to have problems. ...

19 days ago | 1

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Answered
roots of 3*3 matrix determinant
Hi Cern, I assume you mean the three values of w that give a 0 determinant. Eig works for this. K = rand(3,3) c = diag([12 2...

20 days ago | 0

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Answered
LDL does not support complex symmetric matrices
Hi Nathan, the LDL decomposition works for hermitian matrices. In LDL the D matrix is hermitian, so if A = L*D*L', then A' ...

20 days ago | 1

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fft showing frequency components at double rates
Hi Sina, Here is an observation and a possible answer. If you expand out plot(t,y) (I used xlim([4 4.1]*1e-12) ) there ar...

22 days ago | 0

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Solving set of coupled non-linear ode using ode45
Hi Ajai, The angles appear to be measured from the horizontal, not the vertical. That's because the terms involving g use cos(...

23 days ago | 0

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Energy eigenvalues plot of a Hamiltonian(Weyl)
Hi Vira, The plot has no room for px so I assumed it was zero. px=0 corresponds to E(17,:,:,:). Then everything seems to come...

23 days ago | 0

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Answered
when I am subtracting two same values found out from different equations not giving 0, it is giving imaginary value
Hi Bikram, this is all because of precision issues when dealing with floating point numbers. After running your code, tminusx...

28 days ago | 0

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Answered
Is there a way I can convert image (pixel) values to Raman shift using MATLAB?
Now that the peaks in both pixels and cm^(-1) are provided, you can do a linear fit, which is very close. p = [155.56834, 396.5...

1 month ago | 0

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Why does a sine bandwidth decrease with 1/dur, dur beeing the signal duration
Hi Jonas, I believe what you are seeing is just the natural reciprocal relation between width in the time domain and width in t...

1 month ago | 0

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Answered
PCA output gives NaN after normalizing input matrix
Hi Christopher, I am not making any comment on the svd procedure, but f = find(all(obs==0)) f = 79 80 81 82 83 ...

1 month ago | 0

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Answered
How to sort a vector based on the absolute difference of the sorted vector
Hi Awais, a= [2,3,6,12,7,18,25,0,28,5] b = sort(a)' % column vector c = [b(1:end-1) b(2:end)]; d = [diff(c,[],2) ...

1 month ago | 1

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Answered
solve equation in Matlab and for loop
Hi Myrto you have a sixth degree polynomial to solve and find the roots. However, there are no algebraic solutions for the roo...

1 month ago | 0

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Answered
Hankel function, mathematical definition
Hi Kevin, The hankel functions h that you cited are spherical hankel functions, which have half-integer order and are related t...

1 month ago | 1

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Different method of calculation the same thing give different values?
Hi Ariwan, The differences here are all down at the level of machine precision. Differences on the order of 1e-16 happen all t...

2 months ago | 1

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How do I plot an FFT of a large data set?
Hi Angelica, One possible reason is that the data has a DC offset, i.e. its mean is not zero. What can happen is that the DC o...

2 months ago | 0

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Answered
fourier transform shifted graphic
Hello MK First of all it is not a good idea to have a variable called 'sum' because that's the name of a basic Matlab function....

2 months ago | 1

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Answered
Maximize answer of second order Polynomial inequality
Hi Luuk It makes more sense to find the boundaries of the inequality: syms x eqn1 = 0.99*x^2-99==0; x_num = solve(eqn1, x) ...

2 months ago | 1

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Answered
Distribute a sum using binomial distribution
Hi Vorticella, In the code you are using, the two numbers are chosen independently and usually don't add up to be the row sum. ...

2 months ago | 0

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Answered
How to avoid introducing abs( ) when simplifying expressions using the symbolic toolbox ?
Hello Prajwal, norm_v = abs(xdot)/abs(cos(x)) so it does fundamentally depend on abs. Since norm_v is being divided into quan...

2 months ago | 0

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Recurrence relation for polynomial indices
Hello Jaime, Suppose you want the results up to a polynomial of degree p. The following code creates a (p+1)x(p+1) matrix c of...

2 months ago | 0

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Answered
How can I represent the sparse mass, damping and stiffness matrices in state space?
HI 'M', Suppose you have n positions and n corresponding velocities. Let the state space (column) vector be in the order y = ...

2 months ago | 0

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Adding matrices (to assemble global stiffness matrix)
Hi Ryan, here is an example. In the code below, a and b are the indices of the 4x4 submatrix of K that each stiffness submatri...

2 months ago | 0

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David Goodmanson