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# David Goodmanson

### David Goodmanson

658 2012 年以降の合計貢献数

#### David Goodmanson's バッジ

Need help finding the cartesian coordinates of a projectile in flight.
Hi Evan, Assume the two ground positions are p1 and p2. This method uses the 3d triangle p1,p2,and p3 (the intersection point)...

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DFT using matlab function
Hi mk, "Why does the frequency index not change even though the frequency is no longer the nominal value " When you do an ff...

1日 前 | 0

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TE mode trascendental equation problem
Hi Carolina, It's not a real good idea to go with an answer solely on the grounds that 'solve' can find one from an expression ...

5日 前 | 0

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How to use function toi with GHz frequency?
Hi Raul The problem is that you have 32 Hz as a sampling frequency. I assume here that you meant 32GHz. If you look at the ti...

6日 前 | 0

Checking values in a vector
Hello Jose if any(x(4:end)~=0) (do something) else (do something else) end

7日 前 | 0

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solve equation whit integer output as a matrix
Hi Simon, you have z2/z1 = 3.9 % or 10*z2 = 39*z1 since 10 and 39 are relatively prime, i.e. they have no prime factors in...

8日 前 | 0

How to solve a differential equation and the plug a number in for the resulting differential equation
Hi Benjamin, syms x d = diff((1 + 5 * x^2 - 2 * x^3 + 8 * x^4) ^(1/8)) x0 = 8.8 val = double(subs(d,x0)) val = 0.2...

8日 前 | 0

System of nonlinear equations
Hi Aleem, Wolfram Alpha is solving this numercially not analytiaclly so you might as well, too. b = @(t) 10*cosd(15)*(t+ 2*(4...

10日 前 | 1

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My diff function won't work and I'm not sure why
Hi Julia, if you want to use this for a variety of functions, then fun = @(x) exp(2*sin(x)) - x; % one example [f g ...

10日 前 | 0

How to implement polyval in more than one dimension when the summation includes complex coefficients
Hi Matthew, unless I'm missing something, % make up some data M = 5; N = 6; c = rand(N,M)+i*rand(N,M); eps = .3; delt = ...

12日 前 | 0

How can I make curve form data?
Riyadh; The differences from a straight line are small, so it make sense to look at that difference. x = [7000,7050,7100,7150,...

15日 前 | 0

Does fftn do post padding ?
HI raheem, It's pre padding of the original x array by 56 in each dimension, before the fft. As you can see, the y array has n...

15日 前 | 0

Compute the difference matix between a marix and another matrix in MATLAB
Hello Jesujoba, it looks like A and B must have the same number of columns but can have a different number of rows. The for-lo...

16日 前 | 0

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Problem Using Summation Notation with Euler's Number
Hi Jonathan, symbolics is just telling you that it can't do the sum explicitly and get an analytic solution. Fortunately the t...

17日 前 | 0

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Problem in 2 dimensional numerical integration
Hi Ashok, you can make a decent case that the answer is 1/2, at least if the variables are continuous. For the first term, In...

22日 前 | 0

Bessel function - roots and zeros on interval <12,20>
HI Jaroslav Do roots and zeros mean the same thing? The code below uses Newton's method to find the roots, which has the advan...

22日 前 | 0

3D vector plot of electric field
Hello QP, Once you have made the matrix variables XX,YY,ZZ, those are the ones you use for further calculation, no longer x,y,z...

24日 前 | 0

Plotting a matrix of co-ordinates
Hi Anmoi, points = rand(2,56) plot(points(1,:),points(2,:),'o') grid on If you go to the help for plot you will find many ot...

24日 前 | 1

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Matrix division problem on adding condition
Hi David, MODIFIED the solution is not immediate, but you did ask … Take the example A = [1 2 3] C = [5 2 -1] B = the matr...

26日 前 | 2

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Evaluating svd() on slice of matrix array.
Hi Morten I take it that your matrices are close to being orthonomal already. Try [Q, ~] = qr(A(:,:,i)); A(:,:,i) = Q; whic...

How to solve a system of linear equations with strict inequalities and equalities?
Hi Terri, Looks like it is not possible. You have [F1;F2;F3] = [10 2 10 15 20 8 6 4 12] * [x1;...

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How can I solve for the matrix S in the below mentioned matrix equation?
Hello NAA, It appears that you mean that d is 3x6,not 6x3. Let E = EPS_T - EPS_S and abbreviate inv(S) as iS. You are looki...

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How do i scale to my axis after fft?
Hi Cherie, you have a time array of length, 601 and spacing deltat = .01. The frequency array is going to be 601 points with t...

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Raise the elements of a matrix to a power.
Hi Ricardo, min3 = min.^3 It's not a good idea to name a variable 'min' because that is the name of a built-in Matlab function...

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Solving an equation with terms that require double summation and products
Hi GS, I reproduced your results and then calculated the equation using for loops, just to make sure, and got 1.8767e37, same a...

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Solving an equation with terms that require double summation and products
Hi GS, try aij_2 = aij.^2 Since y1 and y2 are scalars, there are three dots in the last equation that you can drop. I usuall...

How to plot double sided amplitude spectrum after FFT?
Hi Hamid, at the end of your code I added the following: figure(2) plot(f,fftshift(cmag),'o'); grid on xlim([-30 30]); f...

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Why are the symbolic units not evaluated by a square root?
Hi Lucas, try your original code but with the last two lines omega_n = (pi/l)^2*(g*E*I/(A*lambda))^(1/2) omega_n = vpa(simpli...

how to calculate direction in rotated coordinate system
Hi UWM, Assuming the correct rotation has already been made, then calling the resulting vector u, and making sure it is normali...

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Why did i get different answers for eigenvectors for different powers of a matrix?
Hi RMT, Since you have two identical eigenvalues, the eigenvectors corresponding to those eigenvalues are not unique*. They on...

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