logo
down
shadow

Calculate the Fourier series with the trigonometry approach


Calculate the Fourier series with the trigonometry approach

By : user2953695
Date : November 21 2020, 01:01 AM
With these it helps Consider developing your code in a different way, block by block. You should be surprised if a code like this would work at the first try. Debugging is one option, as @tom10 said. The other option is rapid prototyping the code step by step in the interpreter, even better with ipython.
Above, you are expecting that b_1000 is non-zero, since the input f(x) is a sinusoid with a 1000 in it. You're also expecting that all other coefficients are zero right?
code :


Share : facebook icon twitter icon
How to calculate a Fourier series in Numpy?

How to calculate a Fourier series in Numpy?


By : user2482111
Date : March 29 2020, 07:55 AM
I wish this help you In the end, the most simple thing (calculating the coefficient with a riemann sum) was the most portable/efficient/robust way to solve my problem:
code :
def cn(n):
   c = y*np.exp(-1j*2*n*np.pi*time/period)
   return c.sum()/c.size

def f(x, Nh):
   f = np.array([2*cn(i)*np.exp(1j*2*i*np.pi*x/period) for i in range(1,Nh+1)])
   return f.sum()

y2 = np.array([f(t,50).real for t in time])

plot(time, y)
plot(time, y2)
Fourier Series from Discrete Fourier Transform

Fourier Series from Discrete Fourier Transform


By : user3015790
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further I'm trying to recreate a function from a discrete fourier transform. In Matlab it would be done like this: , You were running two nested loops instead of one. Try this:
code :
y = ([(dft[nn].real)*np.cos(np.pi*x*nn) + (dft[nn].imag)*np.cos(np.pi*x*nn) for nn in range(0,n)])
Trigonometry functions from series expansion

Trigonometry functions from series expansion


By : Manoj
Date : March 29 2020, 07:55 AM
I wish this helpful for you You can avoid recalculating x**n and the factorial at each step by calculating the next term of the sum using the previous one:
code :
def sin2(x, n=20):
    curr =  x
    res = curr 
    for i in range(2, n, 2):
        curr *= - x**2/(i*(i+1))
        res += curr
    return res
from math import factorial

def sin(x, n=20):
    return sum(x**j/factorial(j)*(1 if i%2==0 else -1)
               for i, j in enumerate(range(1, n, 2)))


%timeit sin(0.7)
# 100000 loops, best of 3: 8.52 µs per loop
%timeit sin2(0.7)
# 100000 loops, best of 3: 4.54 µs per loop
def sin3(x, n=20):
    curr =  x
    res = 0
    minus_x_squared = - x**2
    for i in range(2, n, 2):
        res += curr
        curr *= minus_x_squared/(i*(i+1))
    return res

%timeit sin2(0.7)
# 100000 loops, best of 3: 4.6 µs per loop

%timeit sin3(0.7)
# 100000 loops, best of 3: 3.54 µs per loop
Modeling a Fourier Series from Discrete Fourier Transform for Extrapolation

Modeling a Fourier Series from Discrete Fourier Transform for Extrapolation


By : user1429804
Date : March 29 2020, 07:55 AM
should help you out The error I see in the code is in the complex multiplication: you multiply the real component of the frequency-domain sample with cos, and the imaginary component with sin. This is not how the complex multiplication works. You need to multiply the complex sample value with the complex value cos + i sin. The complex numbers a+ib and c+id, when multiplied, yield ac-bd+iad+ibc, not ac+bd.
code :
N = 250
y = np.cos(np.arange(N)+5)
yf = fft(y)
yf = np.concatenate((yf[:(N+1)//2], np.zeros(N), yf[(N+1)//2:]))
y2 = ifft(yf)
plt.subplot(2,1,1)
plt.plot(y,'.-')
plt.subplot(2,1,2)
plt.plot(y2,'.-')
plt.show()
r programming for loop not working for time series with fourier series

r programming for loop not working for time series with fourier series


By : user3402506
Date : March 29 2020, 07:55 AM
With these it helps The issue seems to be connected with the iterator name i. When I use another iterator, the code works just fine. Unfortunately, I do not exactly understand why this is the case though.
code :
for(j in c(1,2,3,4,5)){
  fit <- tslm(Gas.train~trend + fourier(Gas.train, K = j))
  cat("k = ", j, sep = " ")
  print(CV(fit))
}
Related Posts Related Posts :
  • Remove commas in a string, surrounded by a comma and double quotes / Python
  • How to chain Django querysets preserving individual order
  • Comparison with Python
  • How to find backlinks in a website with python
  • Return new instance of subclass when using methods inherited from parent class in Python
  • Which function in django.contrib.auth creates the default model permissions?
  • Formatting text in tabular form with Python
  • How to determine the first day of a month in Python
  • Error while converting date to timestamp in python
  • Python string iterations
  • Is there any file number limitation when you select multiple files with wxFileDialog?
  • Errors with Matplotlib when making an executable with Py2exe (Python)
  • Django Haystack - Indexing single field
  • Go Pro Hero 3 - Streaming video over wifi
  • Appending a column in .csv with Python/Pandas
  • How to change my result directory in Robot framework using RIDE?
  • problem with using pandas to manipulate a big text file in python
  • python-magic module' object has no attribute 'open'
  • Where goes wrong for this High Pass Filter in Python?
  • Why inserting keys in order into a python dict is faster than doint it unordered
  • flann index saving in python
  • Create new instance of list or dictionary without class
  • How can I easily convert FORTRAN code to Python code (real code, not wrappers)
  • Address of lambda function in python
  • Python adding space between characters in string. Most efficient way
  • python http server, multiple simultaneous requests
  • Disguising username & password on distributed python scripts
  • Post GraphQL mutation with Python Requests
  • Why doesnt pandas create an excel file?
  • Rolling comparison between a value and a past window, with percentile/quantile
  • How to avoid repetitive code when defining a new type in python with signature verification
  • How to configure uWSGI in order to debug with pdb (--honour-stdin configuration issue)
  • In Python, how do you execute objects that are functions from a list?
  • Python- Variable Won't Subtract?
  • Processing Power In Python
  • Python 2.7.2 - Cannot import name _random or random from sys
  • Why doesn't the Python sorted function take keyword order instead of reverse?
  • Make a function redirect to other functions depending on a variable
  • get_absolute_url in django-categories
  • Monitoring non-Celery background task with New Relic in Python
  • Feature selection with LinearSVC
  • LSTM - Predicting the same constant values after a while
  • Test the length of elements in a list
  • Django: render radiobutton with 3 columns, cost column must change according to size & quantity selected
  • Python class attributes vs global variable
  • sys.stdout.writelines("hello") and sys.stdout.write("hello")
  • is ndarray faster than recarray access?
  • Python - search through directory trees, rename certain files
  • GAE: How to build a query where a string begins with a value
  • TypeError: __init__() takes at least 2 arguments (1 given)
  • Overriding and customizing "django.contrib.auth.views.login"
  • Django : Redirect to a particular page after login
  • Python search and copy files in directory
  • pretty printing numpy ndarrays using unicode characters
  • Frequent pattern mining in Python
  • How can I make a set of functions that can be used synchronously as well as asynchronously?
  • Convert one dice roll to two dice roll
  • count occourrence in a list
  • Writing an If condition to filter out the first word
  • to read file and compare column in python
  • shadow
    Privacy Policy - Terms - Contact Us © ourworld-yourmove.org