473,903 Members | 5,463 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

problem with fft periodogram


I am ploting a fft periodogram of my data using a script (found in
internet: http://linuxgazette.net/115/andreasen.html ) that gave me
good results before. There should be a periodicity of >160 in the data
as can be seen by eye. However, this script now says that there is
periodicity of ~9. Can somebody explain me what's wrong? Thank you in
I present first the python script and second my data.
###### usage ############
python <script_name<da ta_file>
######### PYTHON SCRIPT ###########
from scipy import *
import scipy.io.array_ import
from scipy import gplt
from scipy import fftpack
# Read file
f=open(sys.argv[1], 'r')
tempdata = scipy.io.array_ import.read_arr ay(f)
minutes=tempdat a[:,0]
# plot data
gplt.plot(minut es,wolfer,'titl e "Meas" with linespoints')
gplt.xtitle('Mi nutes')
gplt.ytitle('Wo lfer number')
gplt.grid("off" )
power = abs(Y[1:(n/2)])**2
print nyquist
freq=array(rang e(n/2))/(n/2.0)*nyquist
# plot period
gplt.plot(perio d[1:len(period)], power,'title "Simul" with
gplt.xaxis((50, 400))
gplt.xtitle('Pe riod [minutes]')
gplt.ytitle('|F FT|**2')
############### ###########
######## DATA ############
0 48
20 49
40 54
60 49
80 69
100 92
120 98
140 58
160 50
180 66
200 76
220 82
240 119
260 141
280 128
300 107
320 93
340 78
360 74
380 74
400 93
420 109
440 135
460 118
480 90
500 64
520 58
540 56
560 70
580 90
600 115
620 158
640 150
660 96
680 73
700 61
720 55
740 66
760 81
780 116
800 142
820 111
840 102
860 84
880 64
############### ##

Oct 25 '06 #1
1 3809
ai************* @gmail.com wrote:

I am ploting a fft periodogram of my data using a script (found in
internet: http://linuxgazette.net/115/andreasen.html ) that gave me
good results before. There should be a periodicity of >160 in the data
as can be seen by eye. However, this script now says that there is
periodicity of ~9. Can somebody explain me what's wrong? Thank you in
The units are wrong on your period axis. Right now you have them in
units of "sample-spacing". So, the plot is telling you that you have a
periodicity of ~9 sample spacings. To get it in unites of minutes you
need to multiply period by the difference in minutes

period_in_minut es = period * (minutes[1] - minutes[0])

Then, plot period_in_minut es versus power. I see a peak around 180
minutes in your data.


Oct 25 '06 #2

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

by: Bruce Davis | last post by:
I'm having a problem on windows (both 2000 and XP) with a multi-threaded tkinter gui application. The problem appears to be a deadlock condition when a child thread pops up a Pmw dialog window in the context of a main window. The problem does not occur on HPUX or Linux. The following simple example code illustrates the problem and the work around I've come up with; However, I'd like, very much, to get rid of the kludgy work around....
by: Kostatus | last post by:
I have a virtual function in a base class, which is then overwritten by a function of the same name in a publically derived class. When I call the function using a pointer to the derived class (ClassB* b; b->func(); ) the base-class function is called instead of the new function in the derived class. All other similar functions (virtual in the base class and overwritten in the the derived class) work fine, it's just this one function. ...
by: Refky Wahib | last post by:
Hi I need Technical Support I finished a Great project using .Net and SQL Server and .Net Mobile Control My Business case is to implement this Program to accept about 1 Million concurrent users So I designed the project as master Node that has all administration
by: Sudesh Sawant | last post by:
Hello, We have an application which communicates using remoting. There is a server which is a Windows Service. The server exposes an object which is a singleton. The client is a Web Application which makes calls to the service. We are using tcp channel which is using binaryformatter by default. The problem is that after a certain number of remoting calls the calls dont get through to the server. The client application makes the call and...
by: Peter Olcott | last post by:
by: Jon Davis | last post by:
If I have a class with a virtual method, and a child class that overrides the virtual method, and then I create an instance of the child class AS A base class... BaseClass bc = new ChildClass(); .... and then call the virtual method, why is it that the base class's method is called instead of the overridden method? How do I fix this if I don't know at runtime what the child class is? I'm using Activator.CreateInstance() to load the...
by: Ammar | last post by:
Dear All, I'm facing a small problem. I have a portal web site, that contains articles, for each article, the end user can send a comment about the article. The problem is: I the comment length is more that 1249 bytes, then the progress bar of the browser will move too slow and then displaying that the page not found!!!! If the message is less than or equal to 1249 then no problem.
by: Dany | last post by:
Our web service was working fine until we installed .net Framework 1.1 service pack 1. Uninstalling SP1 is not an option because our largest customer says service packs marked as "critical" by Microsoft must be installed on their servers. Now german Umlaute (ä, ü, ö) and quotes are returned incorrectly in SOAP fault responses. This can be easily verified: Implement the following in a web service method (just raises a SOAPException with a...
by: Mike Collins | last post by:
I cannot get the correct drop down list value from a drop down I have on my web form. I get the initial value that was loaded in the list. It was asked by someone else what the autopostback was set to...it is set to false. Can someone show me what I am doing wrong and tell me the correct way? Thank you. In the page load event, I am doing the following:
by: marktang | last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look ! Part I. Meaning of...
by: Hystou | last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it. First, let's disable language synchronization. With a Microsoft account, language settings sync across devices. To prevent any complications,...
by: jinu1996 | last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth. The Art of Business Website Design Your website is...
by: Hystou | last post by:
Overview: Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For most users, this new feature is actually very convenient. If you want to control the update process,...
by: agi2029 | last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own.... Now, this would greatly impact the work of software developers. The idea...
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules. He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms. Adolph will...
by: conductexam | last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one. At the time of converting from word file to html my equations which are in the word document file was convert into image. Globals.ThisAddIn.Application.ActiveDocument.Select();...
by: adsilva | last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
by: 6302768590 | last post by:
Hai team i want code for transfer the data from one system to another through IP address by using C# our system has to for every 5mins then we have to update the data what the data is updated we have to send another system

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.