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David Goodmanson


David Goodmanson

Last seen: Today Active since 2012

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  • Revival Level 3
  • 24 Month Streak
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  • Knowledgeable Level 4
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Answered
Adding matrices (to assemble global stiffness matrix)
Hi Ryan, here is an example. In the code below, a and b are the indices of the 4x4 submatrix of K that each stiffness submatri...

4 days ago | 0

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Answered
Wrong answer being given when adding whole numbers
Hello Matthew, this is happening because the image uses uint8 values (unsigned integer 8 bit), with a range of 0 to 2^8 -1 = 25...

5 days ago | 0

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Answered
How to calculate energy of the signal at a specific frequency after applying FFT
Hello Daniel, To get the desired result you have to be careful about the number of points, so that an exact number of oscillati...

8 days ago | 0

Answered
How to multiply each column in the matrix by different scientific notation values that should be imported from a txt file?
HI Gabrielle, MODIFIED Looks like you have constructing the 128x256 matrix of values covered. The code below converts S{1} to...

9 days ago | 0

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Answered
Using numerical methods to plot solution to first-order nonlinear differential equation
Hello Aleem, You are saying that the analytical solution is not relevant because it involves complex numbers, but that's not th...

10 days ago | 0

Answered
MATLAB determine if matrices are invertible or not
Hi SS P+Q ans = 9 9 2 13 0 0 3 4 -3 -3 6 1 1 1 2 6 det(P+Q) ans = ...

10 days ago | 1

Answered
Solve matrix series equation
Hi Ramesh, This is an overdetermined system, but if you define x as a 2x7 matrix of 2d coordinate values and X as a correspondi...

13 days ago | 0

Answered
interpreting frequency vs phase plot in fft
Hello JL, Since sin(2*pi*f*t) = ( e^(2*pi*i*f*t)-e^(-2*pi*i*f*t) )/(2i), (1) the sine signal has both positive and ...

15 days ago | 0

Answered
Why does the cscvn function of matlab have 4*2*(n-1) coefficients?
Hello Ashkan, factor of (n-1) because n points --> (n-1) intervals, and the polynomials are defined on the intervals factor o...

18 days ago | 0

Answered
Solving a transcendental equation
Hi Kubilay, Finding an algebraic solution for this equation in terms of lambda is not going to happen. But a numerical solutio...

23 days ago | 1

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Answered
How to use Poisson distribution?
Hi Jaya, You appear to be saying that you can't use a loop to increment through event times. For example, though, just before ...

25 days ago | 0

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Answered
I want to treat w as a constant
Hello HJ, try replacing the first line with syms y(x) w real in which case the result is ySol(x) = (exp(-x)*(sin(w*x) + w*c...

27 days ago | 0

Answered
Setting a 3rd vector with specific angles to 2 other vectors
Hi Huseyin, The method you are using gets you into an iterative process of successive rotations about the x and z axis that eve...

1 month ago | 0

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Answered
ODE system with 2 degrees of freedom
Hi Nader, you only need four variables, theta1, theta1dot, theta2, theta2dot (not six). Try function dydt = ODEsystem(t,y) k...

1 month ago | 1

Answered
How to prove the positivity if this function?
Hi Andrea, What might constitute a proof using Matlab is a good question. If the answer to isAlways(y>=0) had come out as 1, w...

1 month ago | 0

Answered
fixing of random number
Hi Irani, If I understand your question correctly, rng(1) Y = randi(10) rng('shuffle') node = randi(20) gives the same val...

1 month ago | 0

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Answered
how to find the angle subtended from origin to the poles in complex plane?
Hello Muhammed, it's as easy as angle(65+65j) angle(65-65j) with each angle in radians subtended from the x axis, -pi < angl...

1 month ago | 0

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Answered
Matlab and Fortran Precision Issue
Hello SA It's the constants. First of all for simplicity I commented out everythng not concerned with calculation of ORIGINAL_...

1 month ago | 0

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Answered
How do you inverse fourier transform 2D data only in one direction?
Hi Gabrielle, I'm not exactly sure what is meant by 'in the x direction' but it sounds like dimension 2. Anyway, ifft(Y,[],2)...

2 months ago | 0

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Answered
Principal Component Analysis: difference between V matrix from SVD decomposition and coef from pca?
Hello Jessica, The set of column vectors that define V in svd, or define coeff in pca, can differ from each other by a factor o...

2 months ago | 0

Answered
extract roll pitch yaw rotation angles from 3D transform
Hello "AT" fwiw, here is a version of finding three rotation angles th1,th2,th3 from a 3d rotation matrix defined below. Ang...

2 months ago | 0

Answered
my question is what is wrong with my code, the results should be in the first picture not the second.
Hi jana, the problem is that the if statements if mod(row,2)==0 && mod(col,2) ==1 && col>=3 % (b) and i...

2 months ago | 0

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Answered
My solver is giving extremely large numbers for a straight forward system of linear equations, what's wrong?
Hi John, What the solver is trying to tell you is that a solution does not exist for this problem, or more correctly it exists ...

2 months ago | 1

Answered
Finding Argument of Bessel Function (1st Kind) to Return Known Solution
Hello 1:5, syms r ex = 5; R = 160; F = besselj(0,(2.405*r)/(R + ex)); Ratio = 0.3005; q = F == Ratio; vpasolve(q,r,[0 ...

2 months ago | 0

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Answered
Multiplication of sparse matrix and a normal matrix
Hi Amit, sum(S)' where the result is still sparse, or full(sum(S)') if you want a regular vector at that point.

2 months ago | 0

Answered
How to find the best fit curve as a vertical scaling of another curve?
Hi SojM, Suppose you have points x,y for the function f(x), where x and y are column vectors. And suppose the red points are t...

2 months ago | 0

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Answered
Solving a system of 4 equations to find the cosine directions from stress matrix and principle stress
Hi Trevor, After taking the terms involving sigma over to the right hand side, the equations are just the eigenvalue equation w...

2 months ago | 0

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Answered
How can i use the ifft() function properly?
Hi Andres, Shifting a function in time by t0 produces a factor of exp(2 pi i f t0) in the frequency domain. In this case it's ...

3 months ago | 1

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Answered
inverse Fourier transform without error problem
Hi MO, It turns out that the variable m is positive in most of its range, but is negative for the array elements >> [min(find(...

3 months ago | 1

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Answered
why the number of point of sfft and istft is different、
Hi neal, The documentation for stft says that if you want the number of sample points to be unaffected, then if length of the ...

3 months ago | 1

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