covariance

问题 This question is a follow up of my previous question: Autofac: Hiding multiple contravariant implementations behind one composite. I'm trying to find the boundries of what we can do with Autofac's covariance and contravariance support. I noticed that Autofac's ContravariantRegistrationSource only supports generic interfaces with a single generic parameter that is marked with the in keyword. This seems to limit the usefulness of this feature, and I'm wondering if Autofac has other ways in

问题 I have been able to calculate covariance for my large data set with: cov(MyMatrix, use="pairwise.complete.obs",method="pearson") This provided the covariance table I was looking for, as well as dealing with the NA issues that are throughout my data. For a deeper analysis, however, I want to create covariance matrices that deal separately with the 800+ groups I have in my data set (some have 40+ observations, others only 1). I tried (from http://www.mail-archive.com/r-help@r-project.org

问题 I'm trying to calculate the mahalanobis distance with c#. I can't find any real good examples online and I'm new to C#. I am especially having trouble getting the covariance matrix to run right. Any help would be appreciated. Thanks! using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using MathNet.Numerics.LinearAlgebra.Double; namespace MahalanobisDistance { class Program { static void Main(string[] args) { Program p = new

问题 I have a X dataset which has 9 features and 683 rows (683x9). I want to take covariance matrix of this X dataset and another dataset which has same shape with X. I use np.cov(originalData, generatedData, rowvar=False) code to get it but it returns a covariance matrix of shape 18x18. I expected to get 9x9 covariance matrix. Can you please help me to fix it. 回答1: The method cov calculates the covariances for all pairs of variables that you give it. You have 9 variables in one array, and 9 more

问题 i'm try to get covariance matrix from an image stored in cv::Mat. i need it for calculate mahalanobis distance and attempt to some color segmentation. this is my code: Mat covar, selection, meanBGR; selection = src(roi); calcCovarMatrix(selection, covar, meanBGR, CV_COVAR_NORMAL|CV_COVAR_ROWS); the Mat src is from webcam and standard BGR opencv format, so CV_32FC3. pixels are stored (i think) in row vector order (blue, green, red).. so i think my code is correct. but i recive this runtime

问题 Given a data matrix data of M dimensions and N samples, say, data = randn(N, M); I could compute the covariance matrix with data_mu = data - ones(N, 1)*mean(data); cov_matrix = (data_mu'*data_mu)./N If I use the native MATLAB function cov_matrix2 = cov(data) this will always be equal to cov_matrix = (data_mu'*data_mu)./(N-1) That is, the denominator is (N - 1) is one less. Why?? Can you reproduce it? Is this a bug?? I use MATLAB version 7.6.0.324 (2008). 回答1: That is, the denominator is (N -

问题 I'm trying to use polyfit to find the best fitting straight line to a set of data, but I also need to know the uncertainty on the parameters, so I want the covariance matrix too. The online documentation suggests I write: polyfit(x, y, 2, cov=True) but this gives the error: TypeError: polyfit() got an unexpected keyword argument 'cov' And sure enough help(polyfit) shows no keyword argument 'cov'. So does the online documentation refer to a previous release of numpy? (I have 1.6.1, the newest

问题 Disclaimer: I'm not a professional developer, and I'm not intending to become one. Reading book about Java, as I wanted to try Android programming, no previous Java experience whatsoever. I'm reading this book - and I rather like it. I've read part of chapter about generic classes, got to the point where they mention wildcards, and got confused. If B extends A: List<B> is not a subtype of List<A> (as I understand it they're exactly the same) List<? extends B> is a subtype of List<? extends A>

问题 How to Convert IList to IList where SomeObject implements ISomeInterface using covariance in C# 4.0 I have something similar to following IList<Items> GetItems; IList<IItems> items = GetItems() as IList<IItems>; but items is null; the answer here was for pre 4.0: Converting an array of type T to an array of type I where T implements I in C# 回答1: why not simply use IList<Items> GetItems; IList<IItems> items = GetItems().Cast<IItems>().ToList(); 回答2: For this to work as you are thinking then I

问题 So, let's say I have: Public Interface ISomeInterface End Interface Public Class SomeClass Implements ISomeInterface End Class If I have MyList as List(Of SomeClass) , I cannot directly set a List(Of ISomeInterface) = MyList . However, I can Set an IEnumerable(Of ISomeInterface) = MyList . With my understanding of Covariance I thought that it should work list to list since List(Of T) implements IEnumerable(Of T) . Clearly, I am missing something. Why does it work that way? Specifically why