Community Profile # David Goodmanson

### David Goodmanson

Last seen: Today Active since 2012

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fft vs nufft- scaling
Hi Nathan, In the fft case you are dividing by N = 1500 and multiplying by 2. For nufft you aren't doing that. Hence the fact...

3 days ago | 0

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Why I got the dominant frequency as 1/time when I running fft?
Hi CS, here is an example, first with 800 points, then 400 points. The frequency scale is constructed differently in each one ...

11 days ago | 0

finding the orthogonal vectors for a series of vectors
Hi Pouya, Here is another method, somewhat related to Bruno's a = 2*rand(1000,3)-1; m1 = tril(ones(3,3)) -triu(ones(3,3)) ...

14 days ago | 1

spline for corner object
HI Mehri, try sorting by angle around a point in the center: x0 = 350; y0 = 325; theta = atan2(y-y0,x-x0); [~,ind] = sort(t...

15 days ago | 1

I want to solve this couple differential where the dot represent the derivative with respect to t/tp, where tp = 30E-9, is my code for solving this is correct? ?
Hi Sahil, Since the constants are all of order 10^-3 to 10^3 or so, it's evident that normalized units are in play. So you hav...

16 days ago | 0

Write a vectorial function from a scalar function
Hi Giuseppi, it looks like you intend, in this case, f = @(z,y) z.^2 + y^2 Here .^ gives the element-by-element square of z, ...

16 days ago | 0

What is the use case for ifft's trailing zero padding? Why is that the default?
Hi Kevin. Zeropaddinig has consequences. It also has its uses, but sometimes the results are unexpected. First of all, whatev...

21 days ago | 1

Why is it giving me undefined function for the slope field?
Hello Brenda, As an alternative to figuring out how to get that code up and running, or as a comparison, you can run your own c...

30 days ago | 0

How to code this quadratic minimization problem subject to a linear constraint?
Hi Armando/Bianca Suppose lambda is a 1x3 row vector. The code below is based on the fact that the solution abc (which is the ...

1 month ago | 0

Interpolation of the values of points on the surface created by convex hull
Hi Jose/Nima, Suppose you have a triangle with vertex points p1, p2, p3, each of those defined by a column vector of their x,y,...

1 month ago | 0

generate white gaussian noise
Hi HL, Since white gaussian noise is just random draws from a normal distribution, you don't really need some toolbox or other,...

1 month ago | 0

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Signal compensation of Time signal via FFT and cable loss frequency spectrum
Hi Michael, Although the Nyquist frequency is N/(2*delta_t), you have to consider both positive and negative frequencies. Assu...

1 month ago | 0

calculation code of PSD using fft
Hi DK, Since you are after power spectral density, and not the spectrum of the linear quantity fft(x), this means the square of...

2 months ago | 0

precision of double variables
Hi Arda, you pretty much answered the question by mentioning precision. Most floating point numbers are not represented exactl...

2 months ago | 1

My code is giving only one solution to a function although there are two solutions, what can I do to get all the solutions?
Hi JN, syms x; assume(x,'positive') and proceed as before for the second one. It is not a great idea to use 'roots' as the n...

2 months ago | 1

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plotting T-U diagram using XSteam
Hi Aldan, the code is running through all the values, but it's not saving any of them. You need to do something like m = 220;...

2 months ago | 1

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I want to highlight the curve of intersection of the sphare and the plane x+y+z=0 by a thick blue curve. How to do that?
Hi Atom, Your code doesn't work because if you multiply out X2^2 + Y2^2 + Z2^2, you don't get R^2. So that arc is not on the s...

2 months ago | 0

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How can I change this explicit method code to the implicit method code?
Hi MC I am not sure what is meant by 'implicit method', and while numerical methods are good, there is also the exact expressio...

2 months ago | 0

How to plot the magnitude and the phase of this function f(1/z)=(0.5 + 000i)*z^(−1 )+ (0.2500 − 0.4330i)*z^(−2) + (−0.2500 − 0.4330i)*z^(−3)?
Hello Aisha, technically this equation should read f(z)=(0.5 + 000i)*z.^(−1 )+ (0.2500 − 0.4330i)*z.^(−2) + (−0.2500 − 0.4330i...

3 months ago | 0

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How to Plot Ramsey Phase Plane
HI ec, There are a couple of issues here. First, the cdot expression lacks a dot, should be k.^(alpha-1). Second, the grid ...

3 months ago | 0

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How the plot of the phase of the complex function look likes BY USING THE MATLAB?
Hi Aisha, Taking the second part first, a phase angle can be either positive or negative. The Matlab angle function uses the u...

3 months ago | 0

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Analytical solution for 1D heat equation
Hi Dominick, you have the sum of two sine terms for the boundary condition, sin(x) and (1/10) sin(10x). So consider a general ...

3 months ago | 0

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Why is 0 and 30 1/2?
Hi Alexander; This occurs because heaviside(-.3:.1:.3) ans = 0 0 0 0.5000 1.0000 1.0000 1.0000 ...

3 months ago | 0

Difference between numerical and analytical solution of ode?
Hi IG, Here is an almost-analytical solution for x0 and x1 (which are called x and y respectively). It's analytic for x, uses ...

4 months ago | 0

I want to plot an implicit equation
Hi mohd, This is not really an implicit equation since Vgs appears only once, by itself, on the lhs. So you can take all the o...

4 months ago | 1

Circular Cross Correlation 2D Using FFT
Hi Ziv, yes, it works similarly. m = 5; n = 6; q = 4; A = randi(m,n,q); B = randi(m,n,q); C = zeros(size(A)); for j = 1:...

4 months ago | 0

How to get coefficients for second degree polynomial with only two given boundary conditions (means with two equations but with three coefficients)?
Hi Ankit, x = [ 0 1 2 3]; E = [0 1 4.5 10.5]; c = polyfit(x,E,2) % fit a quadratic E1 = polyval(c,x) figure(1) plot(x,...

4 months ago | 0

Is there any way to plot values that are exponent multiples of 10 as colorbar directly without having to take their log
Hi Mathan, The colorbars cover the same range in each case, but It's still apples and oranges. Consider the value 1e6 In log sp...

4 months ago | 1

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Can anyone help me? How can I solve 4th order Ordinary differential equations (ODEs)?
Hi Jihweon, Fortunately the analytic solution is pretty straightforward. Denoting Sp by A, the A^-4 factor matches up with the...

4 months ago | 1

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