## Algorithms to find stuff a user would like based on other users likes

I’m thinking of writing an app to classify movies in an HTPC based on what the family members like.

I don’t know statistics or AI, but the stuff here looks very juicy. I wouldn’t know where to start …

## Root mean square function in R

A very brief question.
After much searching I couldn’t find a function to calculate the RMS of a set of integers. Does such a function exist in R?

## how to calculate the Euclidean norm of a vector in R?

I tried norm, but I think it gives the wrong result. (the norm of c(1, 2, 3) is sqrt(1*1+2*2+3*3), but it returns 6..

x1 <- 1:3 norm(x1) # Error in norm(x1) : 'A' must be a numeric matrix norm(as....

## Where to find .NET version usage statistics?

There are some technologies like LINQ and WPF which are nice, but installation of .NET 3.5 is still slow procedure. It’s important to understand – among Windows users how many of them have .NET 3.5 …

## Correlation of Two Variables in a Time Series in Python?

If I have two different data sets that are in a time series, is there a simple way to find the correlation between the two sets in python?

For example with:

# [ (dateTimeObject, y, z) … ]
x = [ (8:…

## Reproduce Fisher linear discriminant figure

Many books illustrate the idea of Fisher linear discriminant analysis using the following figure (this particular is from Pattern Recognition and Machine Learning, p. 188)
I wonder how to reproduce …

## Using perl to find median, mode, Standard deviation?

I have an array of numbers. What is the easiest way to calculate the Median, Mode, and Std Dev for the data set?

## Logistic Regression giving incorrect results

I am working on a website where I collect the results of chess games that people have played. Looking at the ratings of the player and the difference between their rating and that of their opponent, …

## Different standard deviation for same input from Wolfram and numpy

I am currently working on reimplementing some algorithm written in Java in Python. One step is to calculate the standard deviation of a list of values. The original implementation uses …

## What’s the best way to monitor your REST API?

I’ve created an API based on the RESTful pattern and I was wondering what’s the best way to monitor it? Can I somehow gather statistics on each request and how deep could I monitor the requests?