David Goodmanson

Last seen: Today | Active since 2012

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why FFT result and IFFT result has diffrent in very small value? how to avoid this to increase precission?
Hi nirwana, This is totally normal behavior, just computation being computation. Matlab uses double precision arithmetic with ...

6 days ago | 0

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Finding positive-, negative- and zero-sequence components in Matlab
Hi Ygor, I believe the problem is that you are going too soon to real values for Ua,Ub,Uc. In Ua = ((exp(1i.*w1.*t)+exp(-1i.*...

13 days ago | 1

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How to solve such integrations on MATLAB?
Hi simran, for any general function f(z) and a set of points [z1, z2, z3 ...] that describes a path in the complex plane (not n...

14 days ago | 0

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How to do LU factorization without permutation？ The lu() is with permutation.
Hi Alvin Certainly you can do the decomposition without permutation, just not with Matlab lu. (Why you might want to is a diff...

15 days ago | 1

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Period of a Linear Congruential Random Number Generator
HI William. If you're still listening, then if you are only interested in the period and not all of the values of x along the w...

21 days ago | 0

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Dot product of two vector
Hello Syazana syms c1 s1 n1 n2 n3 a1 a2 a3 real A = [c1 -s1 0; s1 c1 0; 0 0 1] A = [c1, -s1, 0] [s1, c1,...

24 days ago | 0

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Solve the integral in the point where the function is singular
Hi Dimani, Leaving out the first '1 ' term that has no singularity and leaving off some constants, you are basically looking at...

1 month ago | 0

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How to generate a noise which sums up as zero?
Hi Ananta, noise=randn(1,64)*sqrt(0.001)*240 noise = noise - mean(noise); if you subtract off the mean, then the new sum of t...

2 months ago | 0

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Trying to use modified secant method to solve for a theta over different g values.
Hi Carson, let b = g*d^2/(2*v^2) % a distance then your equation (multiplied by -1) is b/cos^2 - d*tan - y = 0 plug in ...

2 months ago | 0

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I require frequency response from transfer function = 1/(s^2+(b/m)*s+k/m) where b= 0.0011, k= 87.88 , m = 0.99 in matlab and i need freq in khz
Hi sia, there is not much need to do any detailed calculation when your starting point is what it is. This system has a small a...

2 months ago | 0

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Difference between 2 orientations
Hello Jonathan, You have two 3x3 rotation matrices, each expressed in terms of euler angles, Rrpha(:,1:3) = [cp.*ch, -sp, cp...

2 months ago | 0

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Can't tell if exprnd is working correctly
Hi Umberto, I believe the issue happens because you are plotting the cumulative variables D1 and D2. Once the difference D1-D2...

3 months ago | 0

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Raising a large sparse matrix to a large power
Hi if you are operating on 'a particular vector' v then you do not have to iterate as in m = m*m % iterate to form ...

3 months ago | 2

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I’m thinking of make a command to change Hankel matrix into x time series
Hi Ahmed, here is one way y = magic(5) n = size(y,2); x = zeros(1,2*n-1); x(1:2:end) = diag(y).'; x(2:2:end) = diag(y,1)...

3 months ago | 0

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How to find the width of a peak where there is no actual data, just individual points?
Hi Alfredo, Usually your ydata would be the frequency domain version of a linear quantity such as voltage or displacement. Hal...

3 months ago | 1

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why the simulation period is wrong about schrodinger equation in a harmonic potential
Hi Daniel, Nice animation. Looks like in your 'hamiltonian' function, the kinetic energy is missing a factor of 1/2. Changing...

3 months ago | 0

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Answered
Units for Thermal PDE thermalProperties Function
Hi Simon, The heat conduction equation is dT/dt = alpha (d^2/dx^2+d^2/dy^2+d^2/dz^2) T where alpha, the thermal diffusivity, ...

3 months ago | 0

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Answered
solve 4 equations with some unknown coefficients.
Hi Ahmad, If the answers don't have to match up with the paper, that makes things easier. I took four equations very similar t...

3 months ago | 0

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looking for convenient way to extract matrix from 1*n*n
Hi YL, A=zeros(5,5,5) B=squeeze(sum(A,1)); Squeeze removes all singleton dimensions.

4 months ago | 0

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xcorr lag input to time?
Hi Carly, lags is a dimensionless index, so it's in samples (it has to be samples since xcorr has no way of knowing what fs mig...

4 months ago | 0

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Answered
Most efficient way to put vector on the off-diagonal of the blocks of a block matrix
Hi David, MODIFIED see Dyuman's comment to sensibly shorten this original code. n = 4; v = [1 2 3 4 5 6 7 8 9 8 7 6]; % le...

4 months ago | 1

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How can I create a random matrix without repeating any value between column
Hello Wan, all columns contain 1 through 4, and all columns are different a = perms(1:4) % all 24 permutations of 1:4 ...

4 months ago | 1

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Answered
recreating roots of a derivative of bessel funtion of first order
Hi fv, Here is a function for the first q zeros of both Jn(x) and dJn(x) /dx. As an example, to find the first 100 zeros of th...

4 months ago | 1

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Picking Branch Cut of Square Root
Hi bil, Here is a function that does that job. It appears that you want to do the division (a-i)/(a+i) before taking the squar...

4 months ago | 2

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Answered
Find the nonzero maximum frequency corresponding to FFT graph.
Hi Zahra, the peak at zero frequency is because your signal does not have average value of zero, but has a DC offset. To elimi...

5 months ago | 0

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Answered
Find combination of 12 matrix rows, fulfilling certain criterion, from matrix of size 3432 *7
Hi Ernesto, Once you have a single 12x7 solution you can make many more by random element swapping of elements in that matrix. ...

5 months ago | 0

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I know it is a redundant question, but i have no idea why solve keeps returning 0
Hello Andrei, First of all, all these expressions are functions of (x1-x2) and (y1-y2) only. That means if x1,x2,y1,y2 is a so...

5 months ago | 2

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atanh of negative complex numbers
Hi Derek, For the troublesome subplot, try semilogx(f,unwrap(imag(2*x*gamma))/(2*x)) The idea is that the phase is proportion...

6 months ago | 0

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Answered
Solving systems of trig equations
Hi Jon, Here is one method. To come up with values of r and g that work, it appears to be easier to think in terms of R = r^2 ...

6 months ago | 1

Answered
Change the period/frequency of a Van der Pol Oscillator
Hi Alexis, If you want to preserve the shape you will have to have a larger set of parameters. I am taking as given your equa...

6 months ago | 0

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David Goodmanson