Community Profile # David Goodmanson

### David Goodmanson

Last seen: 1日 前 2012 年からアクティブ

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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.

3日 前 | 0

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...

14日 前 | 0

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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...

14日 前 | 1

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 ...

14日 前 | 1

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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...

18日 前 | 1

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...

18日 前 | 2

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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...

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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. ...

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...

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...

2ヶ月 前 | 0

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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 ...

2ヶ月 前 | 1

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...

3ヶ月 前 | 0

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Cconditional subtraction of 2 vectors of different lengths
Hi salah, You can do quite a bit if the two vectors are sorted. Assume you have two sorted vectors sx and sy of length Nx and ...

3ヶ月 前 | 0

Get "Matrix is is singular to working precision" when attempting a global stiffness matrix with four nodes
Hi Declan, I am not sure how you are getting the error message. Running the code with k changed to K d(range) = K(range,range...

4ヶ月 前 | 1

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energy signal
Hi k.v. For a given real signal y(n) of length N, n = 1 to N, the power at any point n is y(n)^2, the average power P is Pave ...

5ヶ月 前 | 0

How can I evaluate a complex definite integral?
Hi Valentin, It's not strictly necessary (see Paul's vpa solution) but it is advantageous to scale things properly before doing...

6ヶ月 前 | 0

How to use sinc function
Hi Ricardo, while it might be nice to have the Signal Processing toolbox, you certainly don't need to buy any toolboxes to do t...

7ヶ月 前 | 0

how to find concave angle between three points
Hi Eliska, One thing that does not seem to be mentioned so far is your use of the norm function on the determinant. That makes...

7ヶ月 前 | 0

calculation error in hyperbolic function
one possibility: (tanh(-10))^2 ans = 1.0000 % correct although tanh(-(10)^2) % traveling parenthesis ans =...

7ヶ月 前 | 0

Partial derivative with respect to x^2
Hi Yadavindu, df/d(x^2) = (df/dx) / (d(x^2)/dx) = (df/dx) / (2*x) which you can code up without the issue you are seeing.

7ヶ月 前 | 1

Solving a system of Non-linear Equations with Complex numbers
Hellol Aravindhan, not solved by Matlab, but a bit of algebra shows that with x(1) = 2000*a x(2) = 2000*b x(3) = theta/5 t...

7ヶ月 前 | 0

Increasing the caclulation speed while using loops
Hi Hamid, Hi Hamid, I have not speed checked this but it should be faster (the range in your example is different from the draw...

7ヶ月 前 | 2

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How to introduce a phase shift to a existing vector
I assume that you are given the oscillatory function V in an array, with no accompanying array for the independent variable to s...

7ヶ月 前 | 0

Average of random variables from two Poisson distributions?
Hi Jonne, I assume you want to look at the distribution for a period of one minute, whenever that might occur. As opposed to l...

7ヶ月 前 | 1

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How to extrapolate a plot?
What is being fitted is T vs. C, with the idea of extrapolating to T=0. The C variable, C=log((A0-A1)./(A-A1)) contains A, wh...

7ヶ月 前 | 0

z transfer function evaluates to inaccurate value near z=1
Hi Ashish, This function, ((1-1/z^2)/(1-1/z))^6 is identically equal to ((z+1)/z)^6 so you can just use that. And it does ...

7ヶ月 前 | 0

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Why am I getting wrong spectrum applying FFT comparing with correct spectrum?
Hi Jiang, There are a couple of things going on here. The expression for FFT is not correct. Since you are taking the real pa...

7ヶ月 前 | 0

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Solve system of equations with some knowns and unknowns in the same matrix
Hi Yusuf, I'm later on an answer (and losing the race more often, to the extent that there is a race, which to be honest there ...

7ヶ月 前 | 0

How can I code a contour integral representation of cosine?
Hi Richard, this integral converges very slowly along the vertical path gamma-i*inf to gamma+i*inf. Convergence depends on wha...

8ヶ月 前 | 1

reverse lookup table from vector multiplikation with unknown vectors
Hello Henning, Assuming that you want column vectors a and b such that their outer product C = a*b' is as close as possible to ...

8ヶ月 前 | 1