histogram

问题 I am trying to access an 3D histogram of a RGB image. But the histogram matrix returns the number of rows and columns equal to -1. I want to iterate through the histogram and check the individual values in the 3D matrix. But, when I check the number of rows and columns in the matrix, I get -1 as shown below. CODE int main( int argc, const char** argv ) { Mat image = imread("fl.png"); int histSize[3] = {8, 8, 8}; float range[2] = {0, 256}; const float * ranges[3] = {range, range, range}; int

问题 I am using Pandas histogram. I would like to set the y-axis range of the plot. Here is the context: import matplotlib.pyplot as plt %matplotlib inline interesting_columns = ['Level', 'Group'] for column in interesting_columns: data['ranking'].hist(by=data[column], normed=True) There is a range argument that can filter x-values, but I am unaware of the y equivalent: hist(by=[column], normed=True, range=[0, 1]) #working argument hist(by=[column], normed=True, y_range=[0, 1]) #hypothetical

问题 I have two variables that I want to compare in a histogram like the one below. For each bin of the histogram the frequency of both variables is shown what makes it easy to compare them. 回答1: You can use the add parameter to hist (see ?hist , ?plot.histogram ): hist(rnorm(1000, mean=0.2, sd=0.1), col='blue', xlim=c(0, 1)) hist(rnorm(1000, mean=0.8, sd=0.1), col='red', add=T) To find out about the add parameter I noticed that in ?hist the ... argument says that these are arguments passed to

问题 I want to plot a color-coded histogram, where I input an array of arrays to represent the elements on the y-axis, while a simple 1D array on the x-axis to represent a phase. The array of arrays to plot on the y-axis has a dimension, let's say, (100, 25) , while the phase on the x-axis has 25 elements. Therefore, 100 is the number of elements that have to be color-coded for each of the 25 phase-bins. I thought numpy.hist2d was suitable for this, but it only takes two same-sized arrays as input

问题 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

问题 Instead of implementing my own I was wondering if anyone knows of a histogram or bag datastructure implementation in Objective-C that I can use. Essentially a histogram is a hashmap of lists where the lists contain values that relate to their hash entry. A good example is a histogram of supermarket items where you place each group of items dairy, meat, canned goods in their own bag. You can then very easily access each group of items according to their type. 回答1: NSCountedSet is a multiset

问题 Is there a way to add a histogram inside the plot area of another plot, but independent of the "base" plot's coordinate system? In my case, I want to add a histogram as a legend to a choropleth map (the histogram would show the number of regions that fall in each class), but the question could just as easily apply to any plot. For example plot(1:10) rect(1, 7, 4, 9, col="gray") Could I make a histogram appear where the gray rectangle is in the above plot? Currently, if I try to create a

问题 I need to plot a vector of numbers. Let's say these numbers range from 0 to 1000. I need to make a histogram where the x axis goes from 100 to 500, and I want to specify the number of bins to be 10. How do I do this? I know how to use xlim and break separately, but I don't know how to make a given number of bins inside the custom range. 回答1: This is a very good question actually! I was bothered by this all the time but finally your question has kicked me to finally solve it :-) Well, in this

问题 I want to segment car plate to get separate characters. I found some article, where such segmentation performed using brightness histograms (as i understand - sum of all non-zero pixels). How can i calculate such histogram? I would really appreciate for any help! 回答1: std::vector<int> computeColumnHistogram(const cv::Mat& in) { std::vector<int> histogram(in.cols,0); //Create a zeroed histogram of the necessary size for (int y = 0; y < in.rows; y++) { p_row = in.ptr(y); ///Get a pointer to the

问题 I have a multidimensional histogram H=histogramdd((x,y,z),bins=(nbins,nbins,nbins),range=((0,1),(0,1),(0,1))) I need to print in an array the values of H which are different from zero and I also need to know the coordinate/the bins where this happens. I am not familiar with tuples. Can you help me? 回答1: use where to find the index of nozeros in H, and use the index to get the coordinate: import numpy as np x = np.random.random(1000) y = np.random.random(1000) z = np.random.random(1000) nbins