# David Goodmanson

### David Goodmanson

Last seen: Today Active since 2012

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Multiplication of submatrices of a matrix
Hi Laura, if I interpret this correctly, you have n rows (I'll use small letters mostly) of the form Anew = [c c*b1 c c*b2 ...

2 days ago | 0

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matrix inverse results different between r2023b and 2021b
Hi QL. you called both the inverse matrices '2021b' so I called the first one F and the second one S (and the orginal matrix is...

4 days ago | 0

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How do I get rid of these weird lines in the surf plot?
Hello Max, It appears that the GetRectGrid function creates points whose order is imcompatible with the reshape functions that ...

7 days ago | 1

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Error in ode45 solution
Hello PS, Assuming the following (before variables get changed around) tv_jk = tv_kj, for all j,k all real de...

13 days ago | 0

reproduces the audio signal after sampling!!!
Hello Vu & Paul, < I took a brief look at the Vaidyanathan.paper and although the decimation process seems clear enough, the 'i...

22 days ago | 1

Matlab got this wrong: Limit as n goes to infinity: (1+(i/n))^(n^2). Matlab says it's exp(2), which is wrong. Pls confirm.
Hi Moses, not every expression has a limit, or should. That's the case here, as anyone can check. For large n the function zi...

25 days ago | 1

Is there a way to create a lot of graphs for a 4D matrix without coding for a ton of individual graphs?
Hi Kitt, Here is one approach. In the example you are using imagsc plots instead of e.g. 1d plots of some state quantity vs. t...

1 month ago | 1

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How can I calculate the integral of associate LegendreP(1,n,theta)*cos(theta)^2 ?
Hello Se, First of all I think you probably mean the integral of P(1,n,cos(theta))*cos(theta)^2 which is what makes sense whe...

1 month ago | 0

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How to solve swallowtail integral
Hello YM, You won't be able to solve this as a closed form function of X,Y,Z but you can find the integral for given values of ...

1 month ago | 0

Trying to ubderstand the power distribution in fft plot
Hello Yogesh, The fact that all the abs(peaks)^2 add up to the expected total is just Parseval's theorem and has really nothing...

2 months ago | 1

How to interpret the amplitude of impulse() results
Hi HG, the large ampltude of the impulse response is correct. (has the original question been edited?) This has to be the cas...

2 months ago | 0

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Find intersections of two sin wave function
Hello ZH The symbol f is a bit overused in your example, but if you have two functions g1 = A*sin(2*pi*f1*t +phi).^2 g2 = A*...

2 months ago | 0

Struggling to decide the sampling frequency for this fft plot
Hi Yogesh, If the time array has spacing delt (which you denote by dt) and the frequency array has spacing delf, then for an N-...

2 months ago | 0

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Why is my 3D Projectile Trajectory not being calculated properly?
Hi Abeljohn, I think the only real issue here is trying to view the trajectory in plot3, If you let the ground be the xy plane...

2 months ago | 1

When this code is executed, 36 separate windows will open. I want the result to be displayed in a window.
Hi Babr, I think this is basically what is intended, taking the plot out of the for loop. close all; clear; clc N = 2048; ...

2 months ago | 0

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Why do the limits of the following two equations have opposite signs? (MATLAB R2024a Update 1 _20240418)
Hello dq, I think the behaviour is reasonably clear. The first example is limit((1-(-1)^n)/n, n, 0) = -pi*i. If you look at ...

2 months ago | 0

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Issue in getting correct probabilities for Landau Zener Problem
Hello Aryaman, I believe your step sizes are too large, but the first issue is, in the for loop you define a=v*t(i)/2; but then...

2 months ago | 0

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periodic angular acceleration of mechabism
Hi Alberto, (modified once more) If you apply a constant torque tau and advance the angle of the crank by an angle u, then you...

2 months ago | 0

What does the period in line 20 ( after v)represent and why is it needed
Hi Bob, f is a vector with 1000 elements and consequently, so is the denominator. The dot allows matlab to divide each of the ...

3 months ago | 0

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Fixed-step size: why doesn't the Nyquist-Shannon sampling theorem work?
Hello Zahara, The Nyquist theorem gives you the bare minimum number of points to describe the oscillation. More points are bet...

3 months ago | 0

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caculate confidence interval from customized pdf
Hello SX, Ordinarily to find the cdfs you would have to use numerical integration. In this case for the normal distributions, ...

3 months ago | 1

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Helmholtz problem in circular disk
Hi Athanasios, the problem is with the table of zeros of the bessel functions. Counting starts with the first nonzero value, s...

3 months ago | 1

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How can it be that my continuous relative phase exceeds 360 degrees?
Hello Suuz, There is nothing inherently wrong with a phase angle of more than 360 degrees. In fact such a phase can be valuabl...

3 months ago | 0

Symbolic derivative in a sum
Hello OG, If you know d/dp G for the elements of G, you can use d/dp G^-1 = -G^-1 (d/dp G) G^-1 which is all right numericall...

3 months ago | 0

Solving complex linear equations with conjugate operations
Hello SB, Any way you look at it you have four independent unknown quantities, but there is some choice of their form. For the...

3 months ago | 0

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Confusing THD value for a Signal without Harmonics
Hi weinan, MODIFIED The thd process widens the peaks, as shown by the plot produced when you invoke thd. When the frequency i...

3 months ago | 1

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I'm trying to get code to show the increase of density from the center outward.
Hi Matthew, you could try a cutaway view (which doesn't represent the sphere as a solid) n = 40; r0 = 5; [x y z] = sphere(n...

4 months ago | 0

Plotting the profile of an airfoil generated by random NACA numbers.
Hello Keaton, I changed the line TT0 = string(:,3:4) to TT0 = string(:,3) since the program does not run otherwise. ...

4 months ago | 0