python - 'complex' object has no attribute '__getitem__' -


i new python , i'm trying python implementation of fft. have been getting above mentioned error while. do?

import numpy import cmath  def twiddle(r,s):     x = (cmath.exp((2*cmath.pi*1j*s)/r))     return x   def fft(signal):     n = len(signal)     if n==1:         return signal     else:         feven=fft([signal[k] k in range(0,n,2)])         fodd=fft([signal[k] k in range(1,n,2)])       l in range (n/2):         f1 = feven[l] + twiddle(n, -l) * fodd[l]         f2 = feven[l] - twiddle(n, -l) * fodd[l]         return f1+f2

when add print statements feven , fodd, , feed in this:

print (fft([4.5, 3.4, 4.7, 3.8, 6.7, 8.0, 4.6, 7.8]))

i get:

traceback (most recent call last):   file "fft.py", line 41, in <module>     print (fft([4.5, 3.4, 4.7, 3.8, 6.7, 8.0, 4.6, 7.8]))   file "fft.py", line 29, in fft     feven=fft([signal[k] k in range(0,n,2)])   file "fft.py", line 34, in fft    f1 = feven[l] + twiddler(n, -l) * fodd[l]  typeerror: 'complex' object has no attribute '__getitem__'

fixing bug

the problem line

return f1+f2

this causes fft return (with complex number f1 + f2), when in fact should returning list. meant, presume, this:

def fft(signal):     n = len(signal)     if n==1:         return signal     else:         feven=fft([signal[k] k in range(0,n,2)])         fodd=fft([signal[k] k in range(1,n,2)])     f1 = [feven[l] + twiddle(n, -l) * fodd[l] l in range (n/2)]     f2 = [feven[l] - twiddle(n, -l) * fodd[l] l in range (n/2)]     return f1+f2

other comments on code

  1. instead of [signal[k] k in range(0,n,2)] can write signal[0:n:2] using python's slice notation. , similarly, instead of [signal[k] k in range(1,n,2)] can write signal[1:n:2].

  2. in fact, since n length of list signal, can omit since that's default behaviour slices. can write:

    feven = fft(signal[::2]) fodd = fft(signal[1::2])

  3. it doesn't make sense have of "else" code inside else: clause , outside. put in 1 or other.

  4. since fodd numbers multiplied twiddle factor, why not once instead of twice? perhaps this: 

    def fft(signal):     n = len(signal)     if n == 1:         return signal     feven = fft(signal[::2])     fodd = [twiddle(n, -k) * o k, o in enumerate(fft(signal[1::2]))]     f1 = [e + o e, o in zip(feven, fodd)]     f2 = [e - o e, o in zip(feven, fodd)]     return f1 + f2

Comments

Post a Comment

Popular posts from this blog

php - Why I am getting the Error "Commands out of sync; you can't run this command now" -

the documentation of error mentioned in title says if commands out of sync; can't run command now in client code, calling client functions in wrong order. this can happen, example, if using mysql_use_result() , try execute new query before have called mysql_free_result(). can happen if try execute 2 queries return data without calling mysql_use_result() or mysql_store_result() in between. from here: http://dev.mysql.com/doc/refman/5.0/en/commands-out-of-sync.html but in first query not fetching data mysql database, inserting. , in second query getting data database. here code $connection = mysqli_connect("localhost","username","password","tbl_msgs"); if(mysqli_connect_errno($connection)) { die("failed connect mysql: " . mysqli_connect_error()); } $query = "insert users (total_comments, total_views) values ({$total_comments}, {$total_views});"; $query .= "insert msgs (no...
Read more

linux - Does gcc have any options to add version info in ELF binary file? -

i mean whether gcc can insert source code version infor elf binary section or similar. not want change source file, add info gcc option in makefile. you can emit version info text file, turn text file object file statically link executable. the first step simple have write code: script or write version info in format plain text file. write makefile rule produce version.o version.txt, using objcopy . you'll have object file 2 useful symbols defined in it: beginning , end of textual version info. add generated object executable, , you'll able access version 2 ways: running strings on binary, or writing code in application print version string (you'll need declare start , end symbols variables in header file).
Read more

java - Are there any classes that implement javax.persistence.Parameter<T>? -

i'm using named queries fetch entities database using jpa , hibernate , came across puzzling me: how come there no default implementations of javax.persistence.parameter interface? i rather impressed how @staticmetamodel used criteriabuilder in jpa2 meaning type safety , don't have mess around setting string names. wanted apply similar of jpa1 ejb's i'm working on: dealergroup_.class: public dealergroup_ { public parameter<integer> id = new parameterimpl<integer>("id"); /// etc... } dealergroupfacade.class: // ... public dealergroup fetch(integer id) { typedquery<dealergroup> query = em.createnamedquery("dealergroup.fetchbyid", dealergroup.class); query.setparameter(dealergroup_.id, query); return query.getsingleresult(); } // ... i surprised find there no implementations of parameter interface - of course, implement myself absence makes me suspicious may mistake using in way? should implementing parameter...
Read more