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Tuesday, 10 December 2013
Wednesday, 30 October 2013
Fully insane you can watch a video here
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Sunday, 22 September 2013
So I finally discovered the free PowerPivot addin to Microsoft Excel, and wow did my eyes light up at the possibilities. It's like the first time I discovered array formulas or the first time I created a pivot table. Just astonishing. But as with those two previous discoveries came a lot of little issues that eventually sold those technologies short (array formulas are terribly slow when overused, there's years worth of posts on complexity analysis there etc, and pivot tables are extremely limited in their aggregation abilities), I am very wary of getting too excited by this new technology. But so far, it's been pretty good, with a few caveats.
PowerPivot is written by the SQL Server analysis team at MS, and it shows. The spirit of its native language, DAX, is so cube centric, its hard to apply the awkwardly fitted few excel formulas available over the top of the filters - it isn't exactly a love at first sight/match made in heaven. One of the first points that I stumbled at was - there is no native percentile measure in PowerPivot tables. But, since PowerPivot lets you write your own functions using DAX, I decided someone else may have already figured out a decent percentile function to borrow. I was right - the folks over at PowerPivotPro had developed an effective, accurate yet not entirely efficient routine (it would seem the fault lies with the TOPN function they eventually employ - complexity - it's a killer!).
Down to business:-
First you need to create a rank measure. This is easy: =RANKX(ALL(data),[value],,1).
Next, recall that (for excel comparable Percentile estimates) the rank of a percentile is estimated as 1+(n-1)p/100. If you wanted to get tricky, you can use one of the other estimates, such as the Hazen estimate of 0.5+np/100. Just be sure to follow it through all of the formulas.
The next bits are what I've found works the most efficiently and effectively-
This gives you two points to perform a linear interpolation upon, in exactly the same way that percentile.inc (of Excel fame) does.
In part two of this post, I will go into more detail with pictures and exact formulas for various percentiles, including more options for determining ranks, and a non-rank method (or two!)
Tuesday, 21 May 2013
This is the first in a series of articles where I'll be taking a brief look at prediction and forecasting. One of my favorite sites for scientific understanding is Skeptoid.
So I thought we'd take a quick look at some predictions made by Skeptoid around the year 2012 (because we know the other failed predictions!)
Skeptoid predictions for 2012 (from 2008)
Asteroid 433 Eros is going to pass within 17 million miles of the Earth in January;
the United States will hand over control of the Korean military back to the Koreans in April;
<fail - CFC won't be dissolved until at least 2015>
there will be an annular solar eclipse in May and a solar transit of Venus in June;
the Summer Olympics will take place in London;
the Earth's population will officially pass 7 billion people in October;
<fail - world population has reached 7 Billion on October 31, 2011>
the United States will elect a new President in November;
<fail - the us reelected the incumbent president>
construction of the new Freedom Tower will be complete in New York City;
<fail - the freedom tower is still under construction>
the sun will flip its magnetic poles as it does at the end of every 11-year sunspot cycle;<fail - the solar magnetic pole reversal wasn't complete as at December 21 2012 and AFAIK is still underway> and, as I'm sure you've heard by now, the Mayan calendar completes its 5,125 year cycle, <correct>,
Sunday, 5 May 2013
I must say I've been completely wrong about the whole ordeal. My experience was this: I had my Nexus 7 for about 3 months. Totally in love with it, making apps now and then. But then one (fateful?) day I noticed a paper thin scratch on the screen. It seemed to be no big deal, it all still worked. Not long after that however I was playing a game (Sonic CD) and the screen cracked and was no longer responsive in the lower left hand corner (it must have gone through to the digitizer as I would later come to understand).
Well this made the whole thing nigh on useless (I'd have to switch from portrait to landscape and back again just to type things out properly). Games were out of the question. I looked into the warranty and tried to take it back to my retailer to no avail, they said to contact ASUS, and that in general cracked screens are not covered.
I was depressed. I looked into alternative options. Maybe I could try to replace the screen? It seemed costly prohibitive. The cheapest and apparently only option was around the $200 mark after shipping, and then I would have to install it myself. I could buy a new Nexus 7 for not much more than that. Maybe I could sell it on eBay and get like a hundred for it (someone with more technical tenacity than myself was sure to want a bargain.) In the end, I thought, bugger it. I will call ASUS. So I did, and was greeted with a very friendly and helpful customer service rep who said they would send a courier out to pick it up that day. Within 10 days I had a new Nexus 7 arrive on my door step. So despite all of my previous whinging, I'm still a happy owner of a Google Nexus 7 and will continue to make apps when I can (but until I receive my OtterBox Defender Series Hybrid Case with Screen Protector, I will be keeping my Asus Nexus 7 lodged firmly between several pillows.
Monday, 29 April 2013
Tuesday, 16 April 2013