frequency

问题 I am trying to perform FFT on an audio file to find frequency using the Accelerate framework. I have adapted code (probably wrong) from this question: Spectrogram from AVAudioPCMBuffer using Accelerate framework in Swift Although, the magnitudes from ' spectrum ' are either ' 0 ', ' inf ' or ' nan ', and the ' real ' and ' imag ' components of the complex split print similar results; indicating that this is the cause of the problem as: ' magnitude = sqrt(pow( real ,2)+pow( imag ,2) '. Correct

问题 How can I, in R calculate the overall variance and the variance for each group from a dataset that looks like this (for example): Group Count Value A 3 5 A 2 8 B 1 11 B 3 15 I know to calculate the variance as a whole, ignoring the groups I would do: var(rep(x$Value, x$Count)), but how do I automatically calculate the variance for each group accounting for the frequency? E.g., the variance for group A, group B, etc.,.. I would like my output to have the following headers: Group, Total Count,

问题 I have a data.frame mydf with about 2500 rows. These rows correspond to 69 classes of objects in colum 1 mydf$V1 , and I want to count how many rows per object class I have. I can get a factor of these classes with: objectclasses = unique(factor(mydf$V1, exclude="1")); What's the terse R way to count the rows per object class? If this were any other language I'd be traversing an array with a loop and keeping count but I'm new to R programming and am trying to take advantage of R's vectorised

问题 I have a data.frame mydf with about 2500 rows. These rows correspond to 69 classes of objects in colum 1 mydf$V1 , and I want to count how many rows per object class I have. I can get a factor of these classes with: objectclasses = unique(factor(mydf$V1, exclude="1")); What's the terse R way to count the rows per object class? If this were any other language I'd be traversing an array with a loop and keeping count but I'm new to R programming and am trying to take advantage of R's vectorised

问题 Is there a way in php to count how often a value exists in a large array? So if I have an array like this: $array = "1,2,3,4,joe,1,2,3,joe,joe,4,5,1,6,7,8,9,joe"; is there a way to output a new array that tells me (and sorts) which is used most and how many for each? $result = array( [joe] => 4 [1] => 3 [2] =>2 etc... ) I've seen the php array_count_values, but can this be sorted by most -> least? or is there an easier way? Thanks everyone! 回答1: Sort them after counting them with arsort()

问题 I'm looking for a C# source code that performs a frequency analysis on a WAV file and displays the results in a graph, similar to the one displayed in apps like WavePad. Do you know where I can find such a code? Thanks! 回答1: It's in a very experimental state at the moment, but if you have a look at the WPFDemo project in NAudio, it performs an FFT on the incoming microphone data or sound file you play and plots it under the wave-form. 来源： https://stackoverflow.com/questions/1377661/frequency

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 2 years ago . I am new to Pandas, and am trying to use date_range . I came across all kinds of good things for freq , like BME and BMS and I would like to be able to quickly look up the proper strings to get what I want. Yesterday I found a nicely formatted table somewhere in the documentation, but the title of the table was

问题 I'd like to plot a barplot of frequency density of the following ordered categorical data: summary(ACC[EA$TYPE=="A"]) NG SG LG MG HG 2 25 36 17 0 If I plot: plot(ACC[EA$TYPE=="A"]) I get: But I'd like to divide all the values by the total to get a frequency density: Ie. plot(ACC[EA$TYPE=="A"]/sum(as.numeric(ACC[EA$TYPE=="A"]))) but that doesn't work. Any tips? Cheers, 回答1: The default plotting function for a factor is barplot . So if you want a different graph, it may be easier to directly

问题 For my final CS180 project we have been given the task of creating a program that randomly generates some perishable and nonperishable items that would be found in a grocery cart and then printing a receipt for a customer. The problem I am running into is finding a way to check the frequency of an item being created and preventing the item from printing multiple times on a receipt. For example, if someone buys 5 peaches the I want the output to be Peach $.99 X 5, total $4.95, instead of

问题 Can anyone please explain how to perform template matching using FFT. The template is smaller than the original image. 1. Everywhere it states that the template has to be padded with zeros. How it is done. Is it added to the bottom and right of the image or equally around the entire image. Thanks in advance. 回答1: You are using the Fourier Transform to calculate the cross correlation; it's as simple as that. Padding is performed around all sides of the template. This is because a standard Fast