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# David Goodmanson

### David Goodmanson

589 total contributions since 2012

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Cholesky Decomposition Column-Wise Algorithm Implementation
Hi J, I added to the code in your last comment by including the obvious missing 'for' statements, etc. After that, it's pretty...

23 days ago | 1

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scientific notation in each element
Hi c^2, try "format short g" beforehand. Things stay that way until further notice. To go back to the default you can use ...

25 days ago | 0

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FFT of ON OFF signal
Hi imran, you appear to be pretty close on this. The code below uses ftshift to put f = 0 at the middle of the freq array, and...

29 days ago | 0

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Centered FFT & DFT: cannot devise required phase shift vector(s).
Hi Peter, here are some phase shifts. I shortened up some of the variable names to make it easier (for me, anyway) to follow w...

30 days ago | 1

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Why is 1/ones(3,1) OK while 1/ones(1,3) is not OK?
Hi Yuki, In the expression x = 1/ones(3,1) multiplying both sides on the right by ones(3,1) gives x*ones(3,1) = 1. The row ve...

1 month ago | 2

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Bivariate Normal Distribution different for expression and mvnpdf()
Hello Aishwarya, The problem here is that the array x is 2x31 and does not have every possible combination of an element of X1 ...

1 month ago | 2

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How do you find the approximate interval that displays the solution?
Hello Isabel, I believe the idea here is that when lambda is large enough, the expression for Tb gets increasingly close to Tb_...

1 month ago | 0

ODE45 to solve a system of two coupled 2nd order ODEs
Hi Ricardo, I am inferring that you have the following system with fixed points S: S---k1---M---k2---M---k1---S Then eqn 1 is...

2 months ago | 0

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How to element wise exponential of a matrix
Hi Titas, dy = Columns 1 through 10 15.7800 31.5600 47.3400 63.1200 78.9000 94.6800 110.4600 126.2400 142.0200...

2 months ago | 1

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Hello MT, The basic issue is setting phi_3db to degrees, but there may also be a problem with the basic definition of phi_3db (...

2 months ago | 0

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"Fminunc cannot continue" Error with gamma function
Hi Yasin, You can use the gammaln function which is tailor made for this situation.

2 months ago | 1

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How can I find a p-value when dealing with a weighted sum of chi-square distributions?
HI Michael, Since this is a weighted sum instead of a weighted mixture (as I erroneously assumed), the calculation will be alon...

2 months ago | 0

Interpreting xcorr results compared to corrcoef
Hi Jonathan, For the input column vectors, corrcoeff subtracts the mean off of each one and normalizes each to be a unit vector...

2 months ago | 1

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How to generate matrices that satisfies constraints on sum of row elements and sum of column elements?
Hi sharadhi, Here is an example for 3x3, where all the row and column sums are 100 (looks like you edited the original question...

2 months ago | 0

Cumulative distribution function of a function of a random variable
Hi Franziska, a = 1.2; x = .2 y = a*(1+x)*(2/(1+ (1+x)^(1/(a-1))))^(a-1) xx = (y/a)/(2-(y/a)^(1/(a-1)))^(a-1) -1 % ...

2 months ago | 0

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FFT interpolation using zero-padding and the Chirp Z-Transform for a single tone sinusoid
Hi Matt, I made one minor change at the beginning of your code, replacing the first four lines with M = 100; m = linspace(0,1...

2 months ago | 0

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Fourier transform of table signal
Hello fima, It’s true that the amplitude is off, but frequency is a much more serious issue. The time domain plot shows that t...

2 months ago | 0

fourier transform of exp
HI Hadimargo, A few modifications are necessary to make this work out. oo First, in the time domain the exponential function i...

2 months ago | 1

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Generate random numbers from a mixture distribution
Hi Thomas. I presume you mean something like the following. A uniform random variable is used to create an index that picks fr...

3 months ago | 2

How to rotate the plot attached(Truncated Pyramid) to make its sides parallel to its Axis.
Hi adam, two lines become y(m)=R*sind(n+45); x(m)=R*cosd(n+45);

3 months ago | 0

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Trouble with MATLAB Triple Integral
Hi Goerge, The problem with the func([x,y,z]) approach is that there is too much expectation that [x,y,x] is 1x3. Once the int...

3 months ago | 0

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Linear interpolation with multiple values for each point
Hi Justin, If the problem is what I think it is, with d and e known, linear interpolation between o and p determined by a<d<b ...

3 months ago | 0

Problem with the Color Bar
Hi Hans, try colormap(jet) colorbar by default this has 64 color levels (as does the default colormap, 'parula') and looks m...

3 months ago | 1

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Question about fft2(2D Fourier Transform) of a Gaussian function
Hi Zhu Li, A couple of things are going on here. First, there is the checkerboard pattern in the angle plot. I added an extra ...

3 months ago | 1

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The power sum of all frequencies seems that the half amount of the middle frequency power is not added. But the algorithm accords with the Parseval theorem. why?
Hi H^2, It helps that you are doing this for four frequencies rather than some crazy huge number of them. x = 1:4; N = length...

3 months ago | 0

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Problem with symbolic Fourier Transform
Hello Halil, For the delta function, delta(x-x0) = |a| delta(a(x-x0)) so with a = 2*pi, both versions are correct. quick lo...

3 months ago | 1

How does function std process complex numbers
Hi JFz, First of all, for a matrix the std is calculated independently for each column, as is true of many Matlab functions. F...

3 months ago | 1

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Simple squaring of expression
HI Wesley, syms a syms b syms c syms d syms e f = expand((1*a+2*b+3*c+4*d+5*e-8)*(1*a+2*b+3*c+4*d+5*e-8))

3 months ago | 0

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How to solve this equation which contains complex number, bessel equation and its derivative?
Hi bohan shen, The first six roots are shown below. First, since J1 is odd and J0,J2 are even, if z is a root then so is -z. ...

3 months ago | 1

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