standard-deviation

问题 I need a standard deviation function in SQLite. I have found one here: http://www.sqlite.org/contrib?orderby=date but its part of an extension file to SQLite. I've never installed one of these before and I don't know how to. I found this existing function, load_extension , at http://www.sqlite.org/lang_corefunc.html, but I don't understand what the parameters X and Y are. Basically, I need someone to give me a step by step guide on how to install the aggregate extension file. Can anyone do

问题 Normally, I have a more technical problem but I will simplify it for you with an example of counting balls. Assume I have balls of different colors and one index of an array (initialized to all 0's) reserved for each color. Every time I pick a ball, I increment the corresponding index by 1. Balls are picked randomly and I can only pick one ball at a time. My sole purpose is to count number of balls for every color, until I run out of balls. I would like to calculate standard deviation of the

问题 I would like to reproduce the following figure in MATLAB: There are two classes of points with X and Y coordinates. I'd like to surround each class with an ellipse with one parameter of standard deviation, which determine how far the ellipse will go along the axis. The figure was created with another software and I don't exactly understand how it calculates the ellipse. Here is the data I'm using for this figure. The 1st column is class, 2nd - X, 3rd - Y. I can use gscatter to draw the points

问题 This question is intended to both abstract and focus one approach to my problem expressed at "Find the most colourful image in a collection of images". Imagine we have a set of circles, each has a number of points around its circumference. We want to find a metric that gives a higher rating to a circle with points distributed evenly around the circle. Circles with some points scattered through the full 360° are better but circles with far greater numbers of points in one area compared to a

问题 I'm trying to do a simple transformation. I've used the following code and it worked fine: data_stdz <- transform(data_header, z.v1 = v1+2) But, I can't get the following code to work: data_stdz <- transform(data_header, z.v1 = (v1 - mean(v1))/(2*sd(v1)) I've also tried to get just the mean function to work: data_stdz <- transform(data_header, z.v1 = mean(v1) But, I keep getting the following error: Error: unexpected symbol in: "data_std2 <- transform(data_header, z.v1 = mean(v1) data_std2"

问题 I wrote a program which looks up data in a separate txt file and then gives the average and the standard deviation. It finds my average but I get an error for Standard deviation. Was wondering anyone could help me fix my code. This is it: data = File.open("avg_temp.txt", "r+") contents = data.read contents = contents.split("\r\n") #split up array contents.collect! do |x| x.split(',') end sum = 0 contents.each do |x| #make loop to find average sum = sum + x[1].to_f end avg = sum / contents

问题 I have a list: s = [0.995537725, 0.994532199, 0.996027983, 0.999891383, 1.004754272, 1.003870012, 0.999888944, 0.994438078, 0.992548715, 0.998344545, 1.004504764, 1.00883411] where I calculated its standard deviation in Excel, I got the answer: 0.005106477 , the function I used was: =STDEV(C5:N5) Then I do the same calculation using numpy.std as: import numpy as np print np.std(s) However, I got the answer: 0.0048890791894 I even wrote up my own std function: def std(input_list): count = len

问题 Matlab: >> std( [3 2 2 3] ) ans = 0.5774 Layman's interpretation of standard deviation per Google: Mean of {3,2,2,3} = 2.5 Deviation from mean for each value = {0.5, 0.5, 0.5, 0.5} Square of deviation from mean = {0.25, 0.25, 0.25, 0.25} Mean of the squares = 0.25 Square root of 0.25 = 0.5 Therefore Standard Deviation of {3,2,2,3} = 0.5 What did I muck up? I was foolishly expecting those two numbers to agree. 回答1: Matlab std computes the corrected standard deviation. From help std : std

问题 I'm trying to calculate the mean and standard deviation of several columns (except the first column) in a data.frame with NA values. I've tried colMeans , sapply , etc., to create a loop that runs through the data.frame and then stores means and standard deviations in a separate table but keep getting a "FUN" error. any help would be great. Thanks a 回答1: sapply(df, function(cl) list(means=mean(cl,na.rm=TRUE), sds=sd(cl,na.rm=TRUE))) col1 col2 col3 col4 col5 means 3 8 12.5 18.25 22.5 sds 1

问题 I've searched the SQLite docs and couldn't find anything, but I've also searched on Google and a few results appeared. Does SQLite have any built-in Standard Deviation function? 回答1: You can calculate the variance in SQL: create table t (row int); insert into t values (1),(2),(3); SELECT AVG((t.row - sub.a) * (t.row - sub.a)) as var from t, (SELECT AVG(row) AS a FROM t) AS sub; 0.666666666666667 However, you still have to calculate the square root to get the standard deviation. 回答2: The