histogram

Suppose I have two lists: x1 = [1,2,3,4,5,6,7,8,1,10] x2 = [2,4,2,1,1,1,1,1,2,1] Here, each index i of the list is a point in time, and x2[i] denotes the number of times (frequency) than x1[i] was observed was observed at time i . Note also that x1[0] = 1 and x1[8] = 1, with a total frequency of 4 (= x2[0] + x2[8]). How do I efficiently turn this into a histogram? The easy way is below, but this is probably inefficient (creating third object and looping) and would hurt me since I have gigantic data. import numpy as np import matplotlib.pyplot as plt x3 = [] for i in range(10): for j in range

I'm trying to determine if portion of the picture contains red-white striped object (liftramp). If it is present, it looks like this: , and when not like this: The naive approach was to extract histogram, and count if there is more red pixels than blue/green ones: use Image::Magick; my $image = Image::Magick->new; my $rv = $image->Read($picture); #$rv = $image->Crop(geometry=>'26x100+484+40'); my @hist_data = $image->Histogram; my @hist_entries; # Histogram returns data as a single list, but the list is actually groups of 5 elements. Turn it into a list of useful hashes. while (@hist_data) {

I have a continuously generated data (text file) generated by a program on the server. I want to plot the data as a real-time graph just like powergrid does. This was my approach: As the data is generated continuously on the server in a text file, I wrote a PHP script which reads that file( get_file_contents ), outputs the data points and plot the graph using sparkline jQuery plugin. But the problem is that it reads the file all at once . Moreover, the text file keeps on growing. Can anyone suggest me a better approach? As you're talking about using a Javascript plotting solution you do the

I am on the lookout for a faster alternative to R's hist(x, breaks=XXX, plot=FALSE)$count function as I don't need any of the other output that is produced (as I want to use it in an sapply call, requiring 1 million iterations in which this function would be called), e.g. x = runif(100000000, 2.5, 2.6) bincounts = hist(x, breaks=seq(0,3,length.out=100), plot=FALSE)$count Any thoughts? A first attempt using table and cut : table(cut(x, breaks=seq(0,3,length.out=100))) It avoids the extra output, but takes about 34 seconds on my computer: system.time(table(cut(x, breaks=seq(0,3,length.out=100)))