Search Results

Search found 3339 results on 134 pages for 'frequency analysis'.

Page 32/134 | < Previous Page | 28 29 30 31 32 33 34 35 36 37 38 39  | Next Page >

  • C# Freq. Table with Random Values

    - by Sef
    Hello, I am trying to write a frequency program that will represent a bar diagram (in console code). The problem is i have no idea how exactly to caculate this frequency or how do i exactly then give the bars different heights according to there frequency (trough calculation). The frequency height is capped at 21. (meaning the bars go from 1 to 21, so the max bar height would be for example 21 stars(* as display sign for the bar itself). A calculation i have so far (although not sure if correct) for frequency: This array takes the random values generated: for (int j = 0; j < T.Length; j++) { T[j] = (MaxHeight* T[j]) / Ber.GreatestElement(T); Console.Write("{0,7}", T[j]); } This results in values between 0 and 21 -- Based on the values my bars should give a certain height compared to all the other frequency values. (for example 8000 could have 21 in height where 39 could have 1). To represent this diagram i used 2 for loops to display height and width (keep in mind i only wish to use Using System; to keep it to the "basics"). for (int height= 1; height<= 21; height++) { for (int width= 0; width<= 10; width++) { if(...??) { Console.Write("{0,7}", bar); // string bar= ("*"); } else { Console.Write("{0,7}", empty); } } Console.WriteLine(); } So so far i have a entire field filled with * and the random values generated along with their frequency value (although i have no idea if the freq value is properly calculated). I assume i need a if (.....) in the second for but i cannot seem to get further then this. Thanks in advance!

    Read the article

  • Sentiment analysis with NLTK python for sentences using sample data or webservice?

    - by Ke
    I am embarking upon a NLP project for sentiment analysis. I have successfully installed NLTK for python (seems like a great piece of software for this). However,I am having trouble understanding how it can be used to accomplish my task. Here is my task: I start with one long piece of data (lets say several hundred tweets on the subject of the UK election from their webservice) I would like to break this up into sentences (or info no longer than 100 or so chars) (I guess i can just do this in python??) Then to search through all the sentences for specific instances within that sentence e.g. "David Cameron" Then I would like to check for positive/negative sentiment in each sentence and count them accordingly NB: I am not really worried too much about accuracy because my data sets are large and also not worried too much about sarcasm. Here are the troubles I am having: All the data sets I can find e.g. the corpus movie review data that comes with NLTK arent in webservice format. It looks like this has had some processing done already. As far as I can see the processing (by stanford) was done with WEKA. Is it not possible for NLTK to do all this on its own? Here all the data sets have already been organised into positive/negative already e.g. polarity dataset http://www.cs.cornell.edu/People/pabo/movie-review-data/ How is this done? (to organise the sentences by sentiment, is it definitely WEKA? or something else?) I am not sure I understand why WEKA and NLTK would be used together. Seems like they do much the same thing. If im processing the data with WEKA first to find sentiment why would I need NLTK? Is it possible to explain why this might be necessary? I have found a few scripts that get somewhat near this task, but all are using the same pre-processed data. Is it not possible to process this data myself to find sentiment in sentences rather than using the data samples given in the link? Any help is much appreciated and will save me much hair! Cheers Ke

    Read the article

  • What are the frequencies of current in computers' external peripheral cables and internal buses?

    - by Tim
    From Wikipedia, three different cases of current frequency are discussed along with the types of cables that are suitable for them: An Extra Ordinary electrical cables suffice to carry low frequency AC, such as mains power, which reverses direction 100 to 120 times per second (cycling 50 to 60 times per second). However, they cannot be used to carry currents in the radio frequency range or higher, which reverse direction millions to billions of times per second, because the energy tends to radiate off the cable as radio waves, causing power losses. Radio frequency currents also tend to reflect from discontinuities in the cable such as connectors, and travel back down the cable toward the source. These reflections act as bottlenecks, preventing the power from reaching the destination. Transmission lines use specialized construction such as precise conductor dimensions and spacing, and impedance matching, to carry electromagnetic signals with minimal reflections and power losses. Types of transmission line include ladder line, coaxial cable, dielectric slabs, stripline, optical fiber, and waveguides. The higher the frequency, the shorter are the waves in a transmission medium. Transmission lines must be used when the frequency is high enough that the wavelength of the waves begins to approach the length of the cable used. To conduct energy at frequencies above the radio range, such as millimeter waves, infrared, and light, the waves become much smaller than the dimensions of the structures used to guide them, so transmission line techniques become inadequate and the methods of optics are used. I wonder what the frequencies are for the currents in computers' external peripheral cables, such as Ethernet cable, USB cable, and in computers' internal buses? Are the cables also made specially for the frequencies? Thanks!

    Read the article

  • Overriding Object.Equals() instance method in C#; now Code Analysis / FxCop warning CA2218: "should

    - by Chris W. Rea
    I've got a complex class in my C# project on which I want to be able to do equality tests. It is not a trivial class; it contains a variety of scalar properties as well as references to other objects and collections (e.g. IDictionary). For what it's worth, my class is sealed. To enable a performance optimization elsewhere in my system (an optimization that avoids a costly network round-trip), I need to be able to compare instances of these objects to each other for equality – other than the built-in reference equality – and so I'm overriding the Object.Equals() instance method. However, now that I've done that, Visual Studio 2008's Code Analysis a.k.a. FxCop, which I keep enabled by default, is raising the following warning: warning : CA2218 : Microsoft.Usage : Since 'MySuperDuperClass' redefines Equals, it should also redefine GetHashCode. I think I understand the rationale for this warning: If I am going to be using such objects as the key in a collection, the hash code is important. i.e. see this question. However, I am not going to be using these objects as the key in a collection. Ever. Feeling justified to suppress the warning, I looked up code CA2218 in the MSDN documentation to get the full name of the warning so I could apply a SuppressMessage attribute to my class as follows: [SuppressMessage("Microsoft.Naming", "CA2218:OverrideGetHashCodeOnOverridingEquals", Justification="This class is not to be used as key in a hashtable.")] However, while reading further, I noticed the following: How to Fix Violations To fix a violation of this rule, provide an implementation of GetHashCode. For a pair of objects of the same type, you must ensure that the implementation returns the same value if your implementation of Equals returns true for the pair. When to Suppress Warnings ----- Do not suppress a warning from this rule. [arrow & emphasis mine] So, I'd like to know: Why shouldn't I suppress this warning as I was planning to? Doesn't my case warrant suppression? I don't want to code up an implementation of GetHashCode() for this object that will never get called, since my object will never be the key in a collection. If I wanted to be pedantic, instead of suppressing, would it be more reasonable for me to override GetHashCode() with an implementation that throws a NotImplementedException? Update: I just looked this subject up again in Bill Wagner's good book Effective C#, and he states in "Item 10: Understand the Pitfalls of GetHashCode()": If you're defining a type that won't ever be used as the key in a container, this won't matter. Types that represent window controls, web page controls, or database connections are unlikely to be used as keys in a collection. In those cases, do nothing. All reference types will have a hash code that is correct, even if it is very inefficient. [...] In most types that you create, the best approach is to avoid the existence of GetHashCode() entirely. ... that's where I originally got this idea that I need not be concerned about GetHashCode() always.

    Read the article

  • unable to sniff traffic despite network interface being in monitor or promiscuous mode

    - by user65126
    I'm trying to sniff out my network's wireless traffic but am having issues. I'm able to put the card in monitor mode, but am unable to see any traffic except broadcasts, multicasts and probe/beacon frames. I have two network interfaces on this laptop. One is connected normally to 'linksys' and the other is in monitor mode. The interface in monitor mode is on the right channel. I'm not associated with the access point because, as I understand, I don't need to if using monitor mode (vs promiscuous). When I try to ping the router ip, I'm not seeing that traffic show up in wireshark. Here's my ifconfig settings: daniel@seasonBlack:~$ ifconfig eth0 Link encap:Ethernet HWaddr 00:1f:29:9e:b2:89 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:16 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:112 errors:0 dropped:0 overruns:0 frame:0 TX packets:112 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:8518 (8.5 KB) TX bytes:8518 (8.5 KB) wlan0 Link encap:Ethernet HWaddr 00:21:00:34:f7:f4 inet addr:192.168.1.116 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::221:ff:fe34:f7f4/64 Scope:Link UP BROADCAST RUNNING MTU:1500 Metric:1 RX packets:9758 errors:0 dropped:0 overruns:0 frame:0 TX packets:4869 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3291516 (3.2 MB) TX bytes:677386 (677.3 KB) wlan1 Link encap:UNSPEC HWaddr 00-02-72-7B-92-53-33-34-00-00-00-00-00-00-00-00 UP BROADCAST NOTRAILERS PROMISC ALLMULTI MTU:1500 Metric:1 RX packets:112754 errors:0 dropped:0 overruns:0 frame:0 TX packets:101 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:18569124 (18.5 MB) TX bytes:12874 (12.8 KB) wmaster0 Link encap:UNSPEC HWaddr 00-21-00-34-F7-F4-00-00-00-00-00-00-00-00-00-00 UP RUNNING MTU:0 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) wmaster1 Link encap:UNSPEC HWaddr 00-02-72-7B-92-53-00-00-00-00-00-00-00-00-00-00 UP RUNNING MTU:0 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Here's my iwconfig settings: daniel@seasonBlack:~$ iwconfig lo no wireless extensions. eth0 no wireless extensions. wmaster0 no wireless extensions. wlan0 IEEE 802.11bg ESSID:"linksys" Mode:Managed Frequency:2.437 GHz Access Point: 00:18:F8:D6:17:34 Bit Rate=54 Mb/s Tx-Power=27 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=68/70 Signal level=-42 dBm Noise level=-69 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 wmaster1 no wireless extensions. wlan1 IEEE 802.11bg Mode:Monitor Frequency:2.437 GHz Tx-Power=27 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality:0 Signal level:0 Noise level:0 Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 Here's how I know I'm on the right channel: daniel@seasonBlack:~$ iwlist channel lo no frequency information. eth0 no frequency information. wmaster0 no frequency information. wlan0 11 channels in total; available frequencies : Channel 01 : 2.412 GHz Channel 02 : 2.417 GHz Channel 03 : 2.422 GHz Channel 04 : 2.427 GHz Channel 05 : 2.432 GHz Channel 06 : 2.437 GHz Channel 07 : 2.442 GHz Channel 08 : 2.447 GHz Channel 09 : 2.452 GHz Channel 10 : 2.457 GHz Channel 11 : 2.462 GHz Current Frequency=2.437 GHz (Channel 6) wmaster1 no frequency information. wlan1 11 channels in total; available frequencies : Channel 01 : 2.412 GHz Channel 02 : 2.417 GHz Channel 03 : 2.422 GHz Channel 04 : 2.427 GHz Channel 05 : 2.432 GHz Channel 06 : 2.437 GHz Channel 07 : 2.442 GHz Channel 08 : 2.447 GHz Channel 09 : 2.452 GHz Channel 10 : 2.457 GHz Channel 11 : 2.462 GHz Current Frequency=2.437 GHz (Channel 6)

    Read the article

  • Design considerations on JSON schema for scalars with a consistent attachment property

    - by casperOne
    I'm trying to create a JSON schema for the results of doing statistical analysis based on disparate pieces of data. The current schema I have looks something like this: { // Basic key information. video : "http://www.youtube.com/watch?v=7uwfjpfK0jo", start : "00:00:00", end : null, // For results of analysis, to be populated: // *** This is where it gets interesting *** analysis : { game : { value: "Super Street Fighter 4: Arcade Edition Ver. 2012", confidence: 0.9725 } teams : [ { player : { value : "Desk", confidence: 0.95, } characters : [ { value : "Hakan", confidence: 0.80 } ] } ] } } The issue is the tuples that are used to store a value and the confidence related to that value (i.e. { value : "some value", confidence : 0.85 }), populated after the results of the analysis. This leads to a creep of this tuple for every value. Take a fully-fleshed out value from the characters array: { name : { value : "Hakan", confidence: 0.80 } ultra : { value: 1, confidence: 0.90 } } As the structures that represent the values become more and more detailed (and more analysis is done on them to try and determine the confidence behind that analysis), the nesting of the tuples adds great deal of noise to the overall structure, considering that the final result (when verified) will be: { name : "Hakan", ultra : 1 } (And recall that this is just a nested value) In .NET (in which I'll be using to work with this data), I'd have a little helper like this: public class UnknownValue<T> { T Value { get; set; } double? Confidence { get; set; } } Which I'd then use like so: public class Character { public UnknownValue<Character> Name { get; set; } } While the same as the JSON representation in code, it doesn't have the same creep because I don't have to redefine the tuple every time and property accessors hide the appearance of creep. Of course, this is an apples-to-oranges comparison, the above is code while the JSON is data. Is there a more formalized/cleaner/best practice way of containing the creep of these tuples in JSON, or is the approach above an accepted approach for the type of data I'm trying to store (and I'm just perceiving it the wrong way)? Note, this is being represented in JSON because this will ultimately go in a document database (something like RavenDB or elasticsearch). I'm not concerned about being able to serialize into the object above, because I can always use data transfer objects to facilitate getting data into/out of my underlying data store.

    Read the article

  • Learn How to Use Oracle’s Spatial and BI Tools for Location-aware Predictive Analytics

    - by Mandy Ho
    November 29, 2-3pm EST Are you a OBIEE (Oracle Business Intelligence Enterprise Edition) user? Have Location data you'd like to incorporate into your analysis as well? This is a great webinar for you! Join us, as Oracle experts from both teams show how to perform perdictive analytics, network analytics and spatial analysis, combined together, in real world scenarios. We will include demos evaluating airline on-time performance and retail establishment performance.  Learn how to: - Gain better business insights and improve ROI with Oracle Spatial and Graph, Oracle Advanced Analytics, and Oracle Business Intelligence Enterprise Edition (OBIEE). - Streamline and remove the complexity of building applications with OBIEE’s built-in location and analytics features. - Create the statistical model, build interactive reports and dashboards including location analysis and map visualization, and incorporate network analytics for geomarketing and site scoring. - Perform location analysis and processing such as proximity, containment, geocoding, aggregation of geographic regions, and more. Speakers include Jayant Sharma, Director, Product Management, Oracle Spatial and Mapping Technologies; Jean Ihm, Principal Product Manager, Oracle Spatial and Mapping Technologies; and Abhinav Agarwal, OBIEE Product Management. Who should attend This webinar is appropriate for CIOs, business and technical managers, developers, and analysts involved in design and management of analytic applications and solutions where spatial analysis can add insight and value to business processes. Click here, or the link below to sign up today! https://www2.gotomeeting.com/register/764677554

    Read the article

  • Web application Project management methodologie

    - by dutchiexl
    I am looking to streamline my company's web development process. Including analysis. I myself am specialized in XP and Scrum. But we are building web application with a process cycle of 3-4 weeks and a lifetime of 1-4 months. When a project is sold, only then the project managers (= people who do analysis but know nothing about it = a small flow chart and some screen shots as analysis) What is happening is: A LOT of change requests Minimal development time Minimal analysis time NOW: the main question :) can you recommend me some methodologies and books to read for the entire project management ? Thanks in advance @Edit, I myself was looking at a combination of SCRUM for the management with flowcharts, + RAD/LD for development, and trying to distilate something from that.

    Read the article

  • What is Google Page Rank and Why is it So Important?

    What exactly is PageRank? It is basically a link analysis algorithm, which was influenced by citation analysis, which dates way back to the fifties, when it was conceived by Eugene Garfield and later on by Massimo Marchiori. This link analysis algorithm essentially gives set of hyperlinked documents, where they are weighed in numerical form, and are given a number assignment between zero to ten.

    Read the article

  • Computer Networks UNISA - Chap 8 &ndash; Wireless Networking

    - by MarkPearl
    After reading this section you should be able to Explain how nodes exchange wireless signals Identify potential obstacles to successful transmission and their repercussions, such as interference and reflection Understand WLAN architecture Specify the characteristics of popular WLAN transmission methods including 802.11 a/b/g/n Install and configure wireless access points and their clients Describe wireless MAN and WAN technologies, including 802.16 and satellite communications The Wireless Spectrum All wireless signals are carried through the air by electromagnetic waves. The wireless spectrum is a continuum of the electromagnetic waves used for data and voice communication. The wireless spectrum falls between 9KHZ and 300 GHZ. Characteristics of Wireless Transmission Antennas Each type of wireless service requires an antenna specifically designed for that service. The service’s specification determine the antenna’s power output, frequency, and radiation pattern. A directional antenna issues wireless signals along a single direction. An omnidirectional antenna issues and receives wireless signals with equal strength and clarity in all directions The geographical area that an antenna or wireless system can reach is known as its range Signal Propagation LOS (line of sight) uses the least amount of energy and results in the reception of the clearest possible signal. When there is an obstacle in the way, the signal may… pass through the object or be obsrobed by the object or may be subject to reflection, diffraction or scattering. Reflection – waves encounter an object and bounces off it. Diffraction – signal splits into secondary waves when it encounters an obstruction Scattering – is the diffusion or the reflection in multiple different directions of a signal Signal Degradation Fading occurs as a signal hits various objects. Because of fading, the strength of the signal that reaches the receiver is lower than the transmitted signal strength. The further a signal moves from its source, the weaker it gets (this is called attenuation) Signals are also affected by noise – the electromagnetic interference) Interference can distort and weaken a wireless signal in the same way that noise distorts and weakens a wired signal. Frequency Ranges Older wireless devices used the 2.4 GHZ band to send and receive signals. This had 11 communication channels that are unlicensed. Newer wireless devices can also use the 5 GHZ band which has 24 unlicensed bands Narrowband, Broadband, and Spread Spectrum Signals Narrowband – a transmitter concentrates the signal energy at a single frequency or in a very small range of frequencies Broadband – uses a relatively wide band of the wireless spectrum and offers higher throughputs than narrowband technologies The use of multiple frequencies to transmit a signal is known as spread-spectrum technology. In other words a signal never stays continuously within one frequency range during its transmission. One specific implementation of spread spectrum is FHSS (frequency hoping spread spectrum). Another type is known as DSS (direct sequence spread spectrum) Fixed vs. Mobile Each type of wireless communication falls into one of two categories Fixed – the location of the transmitted and receiver do not move (results in energy saved because weaker signal strength is possible with directional antennas) Mobile – the location can change WLAN (Wireless LAN) Architecture There are two main types of arrangements Adhoc – data is sent directly between devices – good for small local devices Infrastructure mode – a wireless access point is placed centrally, that all devices connect with 802.11 WLANs The most popular wireless standards used on contemporary LANs are those developed by IEEE’s 802.11 committee. Over the years several distinct standards related to wireless networking have been released. Four of the best known standards are also referred to as Wi-Fi. They are…. 802.11b 802.11a 802.11g 802.11n These four standards share many characteristics. i.e. All 4 use half duplex signalling Follow the same access method Access Method 802.11 standards specify the use of CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) to access a shared medium. Using CSMA/CA before a station begins to send data on an 802.11 network, it checks for existing wireless transmissions. If the source node detects no transmission activity on the network, it waits a brief period of time and then sends its transmission. If the source does detect activity, it waits a brief period of time before checking again. The destination node receives the transmission and, after verifying its accuracy, issues an acknowledgement (ACT) packet to the source. If the source receives the ACK it assumes the transmission was successful, – if it does not receive an ACK it assumes the transmission failed and sends it again. Association Two types of scanning… Active – station transmits a special frame, known as a prove, on all available channels within its frequency range. When an access point finds the probe frame, it issues a probe response. Passive – wireless station listens on all channels within its frequency range for a special signal, known as a beacon frame, issued from an access point – the beacon frame contains information necessary to connect to the point. Re-association occurs when a mobile user moves out of one access point’s range and into the range of another. Frames Read page 378 – 381 about frames and specific 802.11 protocols Bluetooth Networks Sony Ericson originally invented the Bluetooth technology in the early 1990s. In 1998 other manufacturers joined Ericsson in the Special Interest Group (SIG) whose aim was to refine and standardize the technology. Bluetooth was designed to be used on small networks composed of personal communications devices. It has become popular wireless technology for communicating among cellular telephones, phone headsets, etc. Wireless WANs and Internet Access Refer to pages 396 – 402 of the textbook for details.

    Read the article

  • SSRS 2005 - Usability analysis - Is SSRS a good option for this scenario?

    - by Sach
    How practical is it to consider SSRS 2005 or SSRS 2008 as a reporting solution for a report that has to show reports with millions of records (records vary from 3 to 10 million)? Is there any threshold on the size of report in SSRS? How do I know that for a huge report, wheather SSRS will consume the whole memory and start paging the operations to disk or it will give a memory leak error? Even if I keep on increasing the memory how can I be sure that certain memory will be sufficient for such huge reports for the report server? All the above questions are haunting me because I have a dedicated report server with a decent hardware and OS configuration (8 processors, 8GB RAM, 64 bit OS and 64 bit SQL Server 2005). Still my report with around 2 million records is taking more than 6 minutes and going from one page to another takes 3 minutes!!! My datasource is on separate server and when I execute only the stored proc there, it returns the results in less than 2 minutes.

    Read the article

  • Know of any Java garbage collection log analysis tools?

    - by braveterry
    I'm looking for a tool or a script that will take the console log from my web app, parse out the garbage collection information and display it in a meaningful way. I'm starting up on a Sun Java 1.4.2 JVM with the following flags: -verbose:gc -XX:+PrintGCTimeStamps -XX:+PrintGCDetails The log output looks like this: 54.736: [Full GC 54.737: [Tenured: 172798K->18092K(174784K), 2.3792658 secs] 257598K->18092K(259584K), [Perm : 20476K->20476K(20480K)], 2.4715398 secs] Making sense of a few hundred of these kinds of log entries would be much easier if I had a tool that would visually graph garbage collection trends.

    Read the article

  • How to do a cost-benefit analysis for platform-level features?

    - by Callister Park
    I work on a development team that works closely with Product Managers. There is mutual agreement between the developers and Product Managers that there should be a business case behind every feature the development team builds. My question is, what is an effective way to make a business case for platform-level features that have higher up front cost but will provide long term benefits? For example, the development team would like to implement a plug-in framework. There is the higher up-front cost to implement a plug-in framework but delivering the subsequent features as plug-ins will be cheaper in the long run. This is obvious to everyone including the Product Managers. Is there a standard/simple way to express the cost-benefits? Is there a simple way to visualize it with a graph?

    Read the article

  • How would i down-sample a .wav file then reconstruct it using nyquist? - in matlab [closed]

    - by martin
    Possible Duplicate: How would i down-sample a .wav file then reconstruct it using nyquist? - in matlab This is all done in MatLab 2010 My objective is to show the results of: undersampling, nyquist rate/ oversampling First i need to downsample the .wav file to get an incomplete/ or impartial data stream that i can then reconstuct. Heres the flow chart of what im going to be doing So the flow is analog signal - sampling analog filter - ADC - resample down - resample up - DAC - reconstruction analog filter what needs to be achieved: F= Frequency F(Hz=1/s) E.x. 100Hz = 1000 (Cyc/sec) F(s)= 1/(2f) Example problem: 1000 hz = Highest frequency 1/2(1000hz) = 1/2000 = 5x10(-3) sec/cyc or a sampling rate of 5ms This is my first signal processing project using matlab. what i have so far. % Fs = frequency sampled (44100hz or the sampling frequency of a cd) [test,fs]=wavread('test.wav'); % loads the .wav file left=test(:,1); % Plot of the .wav signal time vs. strength time=(1/44100)*length(left); t=linspace(0,time,length(left)); plot(t,left) xlabel('time (sec)'); ylabel('relative signal strength') **%this is were i would need to sample it at the different frequecys (both above and below and at) nyquist frequency.*I think.*** soundsc(left,fs) % shows the resaultant audio file , which is the same as original ( only at or above nyquist frequency however) Can anyone tell me how to make it better, and how to do the various sampling at different frequencies?

    Read the article

  • How would i down-sample a .wav file then reconstruct it using nyquist? - in MATLAB

    - by Andrew
    This is all done in MATLAB 2010 My objective is to show the results of: undersampling, nyquist rate/ oversampling First i need to downsample the .wav file to get an incomplete/ or impartial data stream that i can then reconstuct. Heres the flow chart of what im going to be doing So the flow is analog signal - sampling analog filter - ADC - resample down - resample up - DAC - reconstruction analog filter what needs to be achieved: F= Frequency F(Hz=1/s) E.x. 100Hz = 1000 (Cyc/sec) F(s)= 1/(2f) Example problem: 1000 hz = Highest frequency 1/2(1000hz) = 1/2000 = 5x10(-3) sec/cyc or a sampling rate of 5ms This is my first signal processing project using matlab. what i have so far. % Fs = frequency sampled (44100hz or the sampling frequency of a cd) [test,fs]=wavread('test.wav'); % loads the .wav file left=test(:,1); % Plot of the .wav signal time vs. strength time=(1/44100)*length(left); t=linspace(0,time,length(left)); plot(t,left) xlabel('time (sec)'); ylabel('relative signal strength') **%this is were i would need to sample it at the different frequecys (both above and below and at) nyquist frequency.*I think.*** soundsc(left,fs) % shows the resaultant audio file , which is the same as original ( only at or above nyquist frequency however) Can anyone tell me how to make it better, and how to do the sampling at verious frequencies?

    Read the article

  • DSP - Filter sweep effect

    - by Trap
    I'm implementing a 'filter sweep' effect (I don't know if it's called like that). What I do is basically create a low-pass filter and make it 'move' along a certain frequency range. To calculate the filter cut-off frequency at a given moment I use a user-provided linear function, which yields values between 0 and 1. My first attempt was to directly map the values returned by the linear function to the range of frequencies, as in cf = freqRange * lf(x). Although it worked ok it looked as if the sweep ran much faster when moving through low frequencies and then slowed down during its way to the high frequency zone. I'm not sure why is this but I guess it's something to do with human hearing perceiving changes in frequency in a non-linear manner. My next attempt was to move the filter's cut-off frequency in a logarithmic way. It works much better now but I still feel that the filter doesn't move at a constant perceived speed through the range of frequencies. How should I divide the frequency space to obtain a constant perceived sweep speed? Thanks in advance.

    Read the article

  • FreqTable with random values(#C)

    - by Sef
    Hello, I would like to make a frequency table with random numbers. So i have created a array that generates 11 random values between 0 and 9999. public void FillArrayRandom(int[] T) { Random Rndint = new Random(); for (int i=0; i < T.Length; i++) { T[i] = Rndint.Next(0, 9999); } }/*FillArrayRandom*/ The result i want is something alike this:(bar height up to 21) So this will be a constant. * * * * * * (the highest value will have the largest row/bar) * * * * 0 1 2 3 .....(index value's) 931 6669 10 8899 .... (up to 11 random values) My question is how do i exactly caculate the frequency between those 11 random values? The bars should have a relative relation with each other depending on there frequency. I would only like to use 1 single array in my program (for the generated values). F = (F * 21?) / ...? Really no clue how to obtain the proper results. If a frequency is =21 write * If a frequency is =20 write * If a frequency is =19 write * etc... Regards.

    Read the article

  • "Most popular" GROUP BY in LINQ?

    - by tags2k
    Assuming a table of tags like the stackoverflow question tags: TagID (bigint), QuestionID (bigint), Tag (varchar) What is the most efficient way to get the 25 most used tags using LINQ? In SQL, a simple GROUP BY will do: SELECT Tag, COUNT(Tag) FROM Tags GROUP BY Tag I've written some LINQ that works: var groups = from t in DataContext.Tags group t by t.Tag into g select new { Tag = g.Key, Frequency = g.Count() }; return groups.OrderByDescending(g => g.Frequency).Take(25); Like, really? Isn't this mega-verbose? The sad thing is that I'm doing this to save a massive number of queries, as my Tag objects already contain a Frequency property that would otherwise need to check back with the database for every Tag if I actually used the property. So I then parse these anonymous types back into Tag objects: groups.OrderByDescending(g => g.Frequency).Take(25).ToList().ForEach(t => tags.Add(new Tag() { Tag = t.Tag, Frequency = t.Frequency })); I'm a LINQ newbie, and this doesn't seem right. Please show me how it's really done.

    Read the article

  • update attribute a element in arraylist on java ?

    - by tiendv
    I have a class Class TextChunks extends Token { ArrayList<Token> arrt = new ArrayList<Token>(); } extent fron class : class Token { String s; int frequency = 1 ;// Tern frequency in TextChunk } Now in token i have arraylist token , i want to update attribute frequency of token in Texchunks when have more than one tokens same . For clearly a give a example : Texchunks :" in particular in domain and range in some " So have 8 token : in,particular,in,domain,and,range,in,some i want update attribute frequency for token : in this example when i get attribute frequency of token "in" must return 3 it mean when i call : get frequency of Texchunks when dislay : in 3 particular 1 in 3 domain 1 and 1 range 1 in 3 some 1 here my code : public TextChunks updateFrequencyOfTokenInTextChunks (TextChunks tc) throws CloneNotSupportedException { TextChunks result = (TextChunks) tc.clone(); for (int i =0 ; i< result.arrt.size() ; i++ ){ int j=i+1; if (result.arrt.get(i).compareTwoToken(result.arrt.get(j))== true ) { // help here how to update attribute result.arrt.get(i) // and result.arrt.get(J) = ++ and } } return tc; } Thanks in advandce

    Read the article

  • DSP - Problems using the inverse Fast Fourier Transform

    - by Trap
    I've been playing around a little with the Exocortex implementation of the FFT, but I'm having some problems. First, after calculating the inverse FFT of an unchanged frequency spectrum obtained by a previous forward FFT, one would expect to get the original signal back, but this is not the case. I had to figure out that I needed to scale the FFT output to about 1 / fftLength to get the amplitudes ok. Why is this? Second, whenever I modify the amplitudes of the frequency bins before calling the iFFT the signal gets distorted at low frequencies. However, this does not happen if I attenuate all the bins by the same factor. Let me put a very simplified example of the output buffer of a 4-sample FFT: // Bin 0 (DC) FFTOut[0] = 0.0000610351563 FFTOut[1] = 0.0 // Bin 1 FFTOut[2] = 0.000331878662 FFTOut[3] = 0.000629425049 // Central bin FFTOut[4] = -0.0000381469727 FFTOut[5] = 0.0 // Bin 3, this is a negative frequency bin. FFTOut[6] = 0.000331878662 FFTOut[7] = -0.000629425049 The output is composed of pairs of floats, each representing the real and imaginay parts of a single bin. So, bin 0 (array indexes 0, 1) would represent the real and imaginary parts of the DC frequency. As you can see, bins 1 and 3 both have the same values, (except for the sign of the Im part), so I guess these are the negative frequency values, and finally indexes (4, 5) would be the central frequency bin. To attenuate the frequency bin 1 this is what I do: // Attenuate the 'positive' bin FFTOut[2] *= 0.5; FFTOut[3] *= 0.5; // Attenuate its corresponding negative bin. FFTOut[6] *= 0.5; FFTOut[7] *= 0.5; For the actual tests I'm using a 1024-length FFT and I always provide all the samples so no 0-padding is needed. // Attenuate var halfSize = fftWindowLength / 2; float leftFreq = 0f; float rightFreq = 22050f; for( var c = 1; c < halfSize; c++ ) { var freq = c * (44100d / halfSize); // Calc. positive and negative frequency locations. var k = c * 2; var nk = (fftWindowLength - c) * 2; // This kind of attenuation corresponds to a high-pass filter. // The attenuation at the transition band is linearly applied, could // this be the cause of the distortion of low frequencies? var attn = (freq < leftFreq) ? 0 : (freq < rightFreq) ? ((freq - leftFreq) / (rightFreq - leftFreq)) : 1; mFFTOut[ k ] *= (float)attn; mFFTOut[ k + 1 ] *= (float)attn; mFFTOut[ nk ] *= (float)attn; mFFTOut[ nk + 1 ] *= (float)attn; } Obviously I'm doing something wrong but can't figure out what or where.

    Read the article

< Previous Page | 28 29 30 31 32 33 34 35 36 37 38 39  | Next Page >