FAQ Database Discussion Community


How do I calculate the standard deviation between weighted measurements?

statistics,standard-deviation,weighted-average
I have several weighted values for which I am taking a weighted average. I want to calculate a weighted standard deviation using the weighted values and weighted average. How would I modify the typical standard deviation to include weights on each measurement? This is the standard deviation formula I am...

Three-way graph (variable, mean, sd) with ggplot2

r,ggplot2,mean,facet,standard-deviation
I think I have an error in my logic while reproducing a graph I found in this pdf here. It should be fairly easy to do, but I have issues to plot a variable with its mean and standard deviation each in their own graph together, as can be seen...

Calculating Standard Deviation of Array Recursively

java,recursion,arraylist,standard-deviation,helper-functions
My assignment is to use recursion to calculate the standard deviation of an Arraylist. I understand how to calculate standard deviation as I have done it without recursion I just need help implementing recursion. I would like to use a helper function if possible. This is the recursive method and...

Standard Deviation calculation error

python,math,standard-deviation
I am trying to figure out why this process gives me a wrong answer. For [1,2,3,4,5] I am getting 1.2 instead of 1.414 def standard_deviation(number_list): average = sum(number_list) / float(len(number_list)) stdev = 0 for value in number_list: stdev += math.sqrt((average - value)**2) / float(len(number_list)) return stdev standard_deviation([1,2,3,4,5]) ...

MySQL Select Results Excluding Outliers Using AVG and STD Conditions

mysql,statistics,standard-deviation
I'm trying to write a query that excludes values beyond 6 standard deviations from the mean of the result set. I expect this can be done elegantly with a subquery, but I'm getting nowhere and in every similar case I've read the aim seems to be just a little different....

Calculate standard deviation for each variable given in a vector

r,standard-deviation
When I have a vector of strings, and each string corresponds to a variable in a dataframe, how can I easily receive a vector of corresponding standard deviations? Is there something better than a loop? Below an example using mtcars: attach(mtcars) string_vector <- ("mpg", "cyl", "disp") I know how to...

Removing a prior sample while using Welford's method for computing single pass variance

algorithm,math,statistics,variance,standard-deviation
I'm successfully using Welford's method to compute running variance and standard deviation as described many times on Stack Overflow and John D Cook's excellent blog post. However in the stream of samples, sometimes I encounter a "rollback", or "remove sample" order, meaning that a previous sample is no longer valid...

Entity Framework - How to get Standard Deviation using GroupBy?

.net,entity-framework,aggregation,standard-deviation
I'm using entity framework 5, code first fluent API. I've built a simple query with a GroupBy for aggregation: var query = context.Table1 .GroupBy(g => new { Prop1= g.Prop1, Prop2 = g.Prop2 }) .Select(s => new { Prop1= s.Key.Prop1, Prop2= s.Key.Prop2, Avg = s.Average(m => m.Minutes), Min = s.Min(m =>...

Adding Array in Standard Deviation

java,arrays,add,standard-deviation
I'm doing Standard Deviation with 10 random numbers. I have to find the average of the 10 numbers. I then subtract the average and square it. I then have to find the average again and find the square root of the average. For example: 2, 4, 4, 4, 5, 5,...

Looping through a method and using the results

java,loops,methods,average,standard-deviation
I am trying to loop through this method 10 times that searches an array of numbers captures the run time in nano seconds and prints the results. I then want t take the 10 run times and find the average and standard deviation. Is there a way to capture the...

Image Parameters (Standard Deviation, Mean and Entropy) of an RGB Image

matlab,image-processing,rgb,entropy,standard-deviation
I couldn't find an answer for RGB image. How can someone get a value of SD,mean and Entropy of RGB image using MATLAB? From http://airccse.org/journal/ijdms/papers/4612ijdms05.pdf TABLE3, it seems he got one answer so did he get the average of the RGB values? Really in need of any help....

Calculate the 3rd standard deviation for an array

python,numpy,standard-deviation
Say, I have an array: import numpy as np x = np.array([0, 1, 2, 5, 6, 7, 8, 8, 8, 10, 29, 32, 45]) How can I calculate the 3rd standard deviation for it, so I could get the value of +3sigma as shown on the picture below? Typically, I...