C# Math: coefficient of variation

Just a short one again. This time I will explain the coefficient of variation. And once again give you a full code example of how you can implement it in c#.

The coefficient of variation (CV) is a normalized measure of dispersion. It is a measure of consistency indicating the uniformity in the values of the signal from the mean of the signal. A smaller coefficient of variation indicates a more consistent signal. The values are more uniformly dispersed.

Coefficient of variation is useful when comparing data with different units. For example in the SoapSynergy project I am working on I often have to make comparisons between displacement and angles. Since those signals have different units ((centi)meters versus degrees) it is useful to have a dimensionless number to compare with.

The downside of the coefficient of variation is that it is quite sensitive to changes in the mean. So if your signal moves around the 0 (as a sine wave does) making your mean ~=0, the coefficient of variation can quickly jump to near infinite numbers rendering it useless. For this reason I chose to calculate the coefficient of variation using the absolute values of my signals.
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Duplicate movies in XBMC

Duplicate movies in XBMC
Example showing duplicate movies in XBMC
Recently I started noticing that every now and then I had duplicate movies in XBMC. Just like that, after downloading a movie or a new episode of a TV show it would be listed twice, and with (almost) exactly the same details. The first couple of times I noticed the duplicate movies in XBMC I ignored them, who cares, I am just going to watch the show and that’s it. But unfortunately my mind does not work that way… It started to annoy me more and more, so today I started searching the web.

Well, I am glad I can now say I found what was causing the duplicate movies in XBMC for me. There were plenty of Google search results on the topic, but none of them seemed to apply to my situation. In the end it, of course, turned out to be much simpler than all those issues shown to me in Google. So simple as well as specific that I might just as well be the only one ever experiencing this. A you ready for it?
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Very last update of the Grocery List Generator add-on

Grocery List Generator for Firefox
Over the last few days I have received numerous e-mails about the latest Firefox 20.0.1 update (finally) breaking my Grocery List Generator add-on. So that was it I thought, I always expected my extensions to go down one by one, but I always thought they would go just a bit slower. Just losing a feature every now and then, apparently I guessed wrong. The Grocery List Generator simply stopped doing it’s most important thing: Generating a grocery list… And that just did not sit well with me. So call me weak, call it unfair to the users of my other extensions, but I have released one last update for the Grocery List Generator on the GLG website. I will not be releasing it to .
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C# Math: Root Mean Square

When dealing with both positive and negative numbers, especially when dealing with a repetitive signal like a sine wave. The mean I described in the previous article may not be that useful at all because the negative values cancel out the positives. In some cases the average power of a signal is more gives you more information, in those cases you can use the Root Mean Square (also called rms or quadratic mean).

  • Root Mean Square takes the squares of all values and divides them by the number of values. And then taking the square root of that number.

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C# Math: Mean, Variance and Standard Deviation

For my first c# code post I will start of with an easy one: Calculating the mean, the variance and the standard deviation of a set of data using c# math. These 3 functions were the first I had to write when I started on the SoapSynergy project written in c# for analyzing the stability and the flexibility of the human motor system.

  • The mean is just the average, the value that is the sum of all values, divided by the number of values.
  • The variance is a way to measure how far a set of numbers is spread out. The variance is an measure of how much a set of numbers change, how much variation there is in those numbers.
  • The standard deviation measures how far the values in a set are spread out from the average, just as the variance does. But since the SD (standard deviation) uses the same units as the mean it is easier to interpret.

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OpenELEC 3.0.0 released

OpenELEC 3.0.0 (Aeon Nox skin)OpenELEC, the embedded OS build around XBMC, has recently released build 3.0.0, the stable build to support XBMC Frodo 12.1. The update can be downloaded here, short update instructions are listed at the end of this post.

The most notable changes from the 1658 (!) changes in total are:

  • DTS-MA and Dolby True-HD via XBMC’s new AudioEngine (requires hardware support, and not possible on AMD and RPi/ATV)
  • Greatly improved Live TV and PVR support
  • Improved image support, allowing the database to use additional image types.
  • Support for the Raspberry Pi
  • Better Airplay support across all platforms
  • Advanced Filtering in the library
  • Advanced UPnP sharing

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New website live

Now that I have quit developing Firefox extensions it was time for a new website as well. Still tweaking things left and right, but I have been doing that for the past few months so now is as good a time as any. I choose for the simplicity of a wordpress website instead of writing an entire site from scratch again, I hope you and I will like it!

End of life for my Firefox extensions

This is the most difficult public announcement I have had to make in a long long time, but this is it people, I am quitting my life as a Firefox extension developer.

I have had the best time developing new things and working closely with the Mozilla community to improve my 10 (!) extensions. But it has been well over 7 years now and it is time for something new. Most of you had already noticed that I was already slowing down on development, and even officially stopped support on some of my extensions. But even inactively maintaining my current 6 extensions is sort of holding me back from really going forward and start doing new things. So it’s time to start shutting things down. Extensions you have currently installed will keep on working as long as Firefox does not change too much. But services around my extension such as my forum or the Web Search Pro search engines pages will be closed sometime in the near future (within a year or so). For Web Search Pro users, mycroft has a huge amount of search engines for you and wont likely close.
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GLG iPhone app website launched

Today the new website of my recipe based grocery list generator for iPhone was launched. The website contains detailed information about the app, and extensive FAQ and youtube videos showcasing the app at work. The recipe based grocery list generator app for iPhone was released 2 months ago but still had to go through life without a proper website. That has ended now with an official “Designed by LX” website suitable for both pc and mobile browsers. Go check out the new site now!