# David Goodmanson

### David Goodmanson

Last seen: Today Active since 2012

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Hi, I am applying findpeaks function to find the peaks of an oscilloscope signal but in the peak plot graph it is automatically changing the x-label with a large difference.
Hi Rikita, if you use findpeaks(y,x) where x is the x axis (linear or log scale) whose min and max match the oscilloscope trace ...

9 dagar ago | 0

Why such a fuss with ndgrid and meshgrid issues?
Hi Kristoffer, I totally agree that Mathworks should use nonsquare examples in the documentation for meshgrid, ndgrid, surf etc...

14 dagar ago | 1

How do I find the phase for a periodic cos wave using fft?
Hi Noam, here is a version using time and frequency in the usual manner. A couple of ponts here. If you construct a grid as y...

20 dagar ago | 0

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how to write the right code to measure the elapsed time of this method d1 = diag(1./diag(A))
Hi Amna, A common way to do this is with tic and toc. So: a = rand(1e4,1e4); tic b = diag(1./diag(a)); toc Elapsed time...

25 dagar ago | 0

using polyval with one of the polynomials of a spline obtained with the unmkpp command, the results do not overlap! Why?
Hello TH,. spline polynomials are local to the secgment in question starting from x = 0, so if an interval is, for example 3 to...

ungefär en månad ago | 1

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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 ...

ungefär en månad 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...

ungefär en månad 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 ...

ungefär en månad 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...

ungefär 2 månader 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...

ungefär 2 månader 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...

ungefär 2 månader 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...

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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...

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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 ...

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...

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...

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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*...

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-...

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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...

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; ...

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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 ...

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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...

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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...

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 ...

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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...

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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, ...

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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...

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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...