Answered

orthagonal planes and normal vectors

Hi M, A plane satisfies the dot product equation equation r dot v = const where r is the position vector [x y z] and v = [vx ...

orthagonal planes and normal vectors

Hi M, A plane satisfies the dot product equation equation r dot v = const where r is the position vector [x y z] and v = [vx ...

5 days ago | 2

| accepted

Answered

How to generate a random complex unitary matrix whose columns each sum up to 1

MODIFIED to replace previous random function Hi Michael, here is one way. It's based on the idea that if the unitary matrix U...

How to generate a random complex unitary matrix whose columns each sum up to 1

MODIFIED to replace previous random function Hi Michael, here is one way. It's based on the idea that if the unitary matrix U...

6 days ago | 1

| accepted

Answered

Solving a 3 degree of freedom mass spring damper model

Hi Z^2, Now that you have the K, C and M matrices, you can create a matrix equation to find the natural resonant frequencies. G...

Solving a 3 degree of freedom mass spring damper model

Hi Z^2, Now that you have the K, C and M matrices, you can create a matrix equation to find the natural resonant frequencies. G...

6 days ago | 0

Answered

Solve for the constants of a Quartic given the complex roots?

Hi Johnathan, r = [-5 -6 -9.6+25.7i -9.6-25.7i]; p = poly(r) r1 = roots(p) % check p = 1.0e+04 * 0.0001 0.0030 ...

Solve for the constants of a Quartic given the complex roots?

Hi Johnathan, r = [-5 -6 -9.6+25.7i -9.6-25.7i]; p = poly(r) r1 = roots(p) % check p = 1.0e+04 * 0.0001 0.0030 ...

6 days ago | 0

| accepted

Answered

Coding a function for the Fourier Transform.

Hi Anthony, the only problem here is the normalization. For the inverse transform you are dividing by sqrt(N) every time, (N b...

Coding a function for the Fourier Transform.

Hi Anthony, the only problem here is the normalization. For the inverse transform you are dividing by sqrt(N) every time, (N b...

6 days ago | 0

| accepted

Answered

Ignoring NaNs for polyfit

Hello TimaMarie, yes, polyfit doesn't like NaNs. One way out is, just before doing polyfit, toss out the elements of both vari...

Ignoring NaNs for polyfit

Hello TimaMarie, yes, polyfit doesn't like NaNs. One way out is, just before doing polyfit, toss out the elements of both vari...

7 days ago | 0

| accepted

Answered

Find first item with a certain condition and use it, instead of finding all items with that condition

Hi Thomas, [After reading comments from Bruno and Rik I realized I forgot to mention that in order to get your code to run I ch...

Find first item with a certain condition and use it, instead of finding all items with that condition

Hi Thomas, [After reading comments from Bruno and Rik I realized I forgot to mention that in order to get your code to run I ch...

8 days ago | 1

Answered

Fzero returning wrong root

Hello Emily If you insert this F_theta = double(F_theta); just after the calculation of F_theta, you will get the correct res...

Fzero returning wrong root

Hello Emily If you insert this F_theta = double(F_theta); just after the calculation of F_theta, you will get the correct res...

8 days ago | 2

| accepted

Answered

Solution of differential equations with an input derivative

Hi Pawel, you have e = -x(1) + 1; so de/dt = d/dt(-x(1) + 1) = -dx(1)/dt but dx(1)/dt = (x(2)-x(1))/T2 so you can replace...

Solution of differential equations with an input derivative

Hi Pawel, you have e = -x(1) + 1; so de/dt = d/dt(-x(1) + 1) = -dx(1)/dt but dx(1)/dt = (x(2)-x(1))/T2 so you can replace...

9 days ago | 1

| accepted

Answered

quat2angle different result

Hi Sven, it's pretty clear that both test and original have discontinuities because the function producing the angles, probably...

quat2angle different result

Hi Sven, it's pretty clear that both test and original have discontinuities because the function producing the angles, probably...

14 days ago | 0

Answered

WHY ARE THE COLORS OF MY LEGEND ALL MESSED UP?

Hi OI, One reason that Sylvain posted his comment is that you do not provide working code. And of course your odds of getting ...

WHY ARE THE COLORS OF MY LEGEND ALL MESSED UP?

Hi OI, One reason that Sylvain posted his comment is that you do not provide working code. And of course your odds of getting ...

15 days ago | 1

Answered

Why do I get too high dominant frequencies in FFT

Hi Timo, From your attached data I can see that it's 2 sec at 48 kHz as you said. In your frequency plot, the data seems to be...

Why do I get too high dominant frequencies in FFT

Hi Timo, From your attached data I can see that it's 2 sec at 48 kHz as you said. In your frequency plot, the data seems to be...

15 days ago | 0

Answered

fitting only continous line

Hi salman, I have been off taking a look at this problem. The method below uses the fact that what you call the discontinouus ...

fitting only continous line

Hi salman, I have been off taking a look at this problem. The method below uses the fact that what you call the discontinouus ...

17 days ago | 0

| accepted

Answered

ilaplace returns unexpected answer

Hi Abdulla, You mention +- 3 as the coefficient, but are using +-6 in the actual example so I will stay with that. Looking at ...

ilaplace returns unexpected answer

Hi Abdulla, You mention +- 3 as the coefficient, but are using +-6 in the actual example so I will stay with that. Looking at ...

18 days ago | 0

| accepted

Answered

Changing the amplitude (y-axis) of an FFT back to units of force.

Hi Kev, The first thing is, the time and frequency arrays have to be correct. You are not actually using the 'time' variable b...

Changing the amplitude (y-axis) of an FFT back to units of force.

Hi Kev, The first thing is, the time and frequency arrays have to be correct. You are not actually using the 'time' variable b...

18 days ago | 1

Answered

How to avoid an Infinite Loop?

Waseem, Nothing in the entire while loop alters either 'sizes' or 'sizesB'. So if sizes(1) ~= sizesB(1), that condition will ...

How to avoid an Infinite Loop?

Waseem, Nothing in the entire while loop alters either 'sizes' or 'sizesB'. So if sizes(1) ~= sizesB(1), that condition will ...

21 days ago | 0

Answered

Calculation of antenna efficiency

Hi Shahar, The plot is of directivity, not gain (confusingly, directivity is sometimes called directive gain). Since directivi...

Calculation of antenna efficiency

Hi Shahar, The plot is of directivity, not gain (confusingly, directivity is sometimes called directive gain). Since directivi...

21 days ago | 0

| accepted

Answered

How can I obtain the mean and standard deviation of a gaussian PDF

Hi Matthew, here is an example, where mu and sigma are calculated by numerical integration. Also shown are analytical results ...

How can I obtain the mean and standard deviation of a gaussian PDF

Hi Matthew, here is an example, where mu and sigma are calculated by numerical integration. Also shown are analytical results ...

23 days ago | 1

| accepted

Answered

Why am I getting Complex number results?

Hello Ethan, The reason for this is that at step i = 14, the quantity on the third to last line, (1-(c*y(i)/T)) becomes negativ...

Why am I getting Complex number results?

Hello Ethan, The reason for this is that at step i = 14, the quantity on the third to last line, (1-(c*y(i)/T)) becomes negativ...

28 days ago | 1

Answered

Poisson Boltzmann eq. with an infinite boundary condition

Hi Roi For convenience I will use u in place of psi. An exact solution is tanh(u/4) = A*exp(-x) where A = tanh(1/4) ...

Poisson Boltzmann eq. with an infinite boundary condition

Hi Roi For convenience I will use u in place of psi. An exact solution is tanh(u/4) = A*exp(-x) where A = tanh(1/4) ...

1 month ago | 1

Answered

Can I use the PDEPE solver to solve the following dimensionless Transient PFR PDE? If not, what method do you reconmend?

Hello Rogelio, For psi(t,eta) I assume that the boundary conditions are psi(0,eta) = 0 for all eta an...

Can I use the PDEPE solver to solve the following dimensionless Transient PFR PDE? If not, what method do you reconmend?

Hello Rogelio, For psi(t,eta) I assume that the boundary conditions are psi(0,eta) = 0 for all eta an...

1 month ago | 0

Answered

double peaks in FFT matlab

Hello hamzah the fft is a complex function. Are you plotting only the real part? This problem is occurring because your delta...

double peaks in FFT matlab

Hello hamzah the fft is a complex function. Are you plotting only the real part? This problem is occurring because your delta...

1 month ago | 0

Answered

How to plot wavelength and wavenumber FFT from intensity data

Hi Arwi, n = 3648, dpix = 8e-9; % 8nm seems small for a pixel width The x array has spacing delx = dpix and is x = delx*(0:...

How to plot wavelength and wavenumber FFT from intensity data

Hi Arwi, n = 3648, dpix = 8e-9; % 8nm seems small for a pixel width The x array has spacing delx = dpix and is x = delx*(0:...

1 month ago | 0

Answered

Verifying the uncertainty principle with fft for Gaussian

Hello Ori, The problem stems from the following, where I am using t and f rather than x and k (see comment). For an fft, once ...

Verifying the uncertainty principle with fft for Gaussian

Hello Ori, The problem stems from the following, where I am using t and f rather than x and k (see comment). For an fft, once ...

1 month ago | 0

| accepted

Answered

why the Real and imaginary part of fourier transform (fft) are not zero for real odd function

Hi Jiali, with an even number of points the symmetry is not quite right. In the frequency domain, for eight points (without an...

why the Real and imaginary part of fourier transform (fft) are not zero for real odd function

Hi Jiali, with an even number of points the symmetry is not quite right. In the frequency domain, for eight points (without an...

1 month ago | 0

| accepted

Answered

How to solve Ax=B with some knowns in x and B

Hi Derek, the method below uses y instead of B so that A*x = y, and does not assume that the known values of x are contiguous t...

How to solve Ax=B with some knowns in x and B

Hi Derek, the method below uses y instead of B so that A*x = y, and does not assume that the known values of x are contiguous t...

1 month ago | 0

Answered

Convert permute and reshape to for

Hi Raquel, For loops are going to be slower, but it is interesting to seet how much and under what circumstances. The followin...

Convert permute and reshape to for

Hi Raquel, For loops are going to be slower, but it is interesting to seet how much and under what circumstances. The followin...

2 months ago | 0

| accepted

Answered

X axis for convoluted function

Hi dinesh, Here is an example with two normal (gaussian) pdfs. Arrays x and f(x) describe one of them, and arrays y and g(y) d...

X axis for convoluted function

Hi dinesh, Here is an example with two normal (gaussian) pdfs. Arrays x and f(x) describe one of them, and arrays y and g(y) d...

2 months ago | 0

Answered

¿Why the phase of the Fourier transform whith "angle" fuction of a rectangular pulse function is not odd?

Hi Paulina, neglecting some unimportant (in this context) real constants, the fourier transform of the square pulse is sin(w*t...

¿Why the phase of the Fourier transform whith "angle" fuction of a rectangular pulse function is not odd?

Hi Paulina, neglecting some unimportant (in this context) real constants, the fourier transform of the square pulse is sin(w*t...

2 months ago | 0

Answered

RF toolkit capacitance calculation

Hi Derek, The exact expression is indeed the acosh expression used in Matlab, and we would expect no less. The log expression ...

RF toolkit capacitance calculation

Hi Derek, The exact expression is indeed the acosh expression used in Matlab, and we would expect no less. The log expression ...

2 months ago | 0

| accepted