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nphrk

52 karma · joined April 1, 2011

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nphrk··on The Central Limit Theorem Visualized with D3
It is the distribution of the average of n binomial distributions (taking on values x±1)†, which according to the CLT converges to a Gaussian as n→∞.

[†] x is where it is centered.

nphrk··on Instagram says it now has the right to sell your photos
The copyright issue can be a bit tricky. Assuming that Instagram goes on and sells users' pictures - who's liable if somebody uploads a picture which he/she doesn't own, and then Instagram goes on and sells that to a third party?
nphrk··on Prismatic gets $15 million in Series A Funding
Great! I love the service, I miss only an app for my Android tablet. Keep up the good work.
nphrk··on Understanding The Fourier Transform
The article uses the magnitude of the coefficients, which is computed using both the real and the imaginary part.
nphrk··on Understanding The Fourier Transform
This is a nice way to see how the DFT is computed, however I find the view of the FT as a change of basis as even more important - generalizes easily to other bases and and one can understand easily wavelets and their advantages. Basically, the sinusoids form a basis of the vector space of functions (every 'non-pathological' function can be written as a possibly infinite sum of them) and the numbers computed by the FT are coefficients for the respective basis vectors - the magnitude of these coefficients is interpreted as the strength of the corresponding wave in the original signal.

Another way to see the FT is as the basis where the convolution operators are diagonal - this is used in image processing, where computing the FFT of a filter + entry-wise multiplication can be much faster than running the convolution at each pixel of the input image.

nphrk··on Ask HN: what was the best life/programming choice you ever made?
Could you recommend some introductory books? I've always felt bad not having clue about art.
nphrk··on Blaze: Next Generation NumPy
There's http://www.videolectures.net, but I think that they only host their own material.
nphrk··on Red Bull Stratos Skydive Rescheduled for today
Just landed!
nphrk··on Infographic: US campaign finances revealed
Very interesting, I have only one nitpick (maybe for the paranoid only) : why not show the cumulative distribution but pick 200$ as a threshold?
nphrk··on Neural Networks for Machine Learning
Well not quite. While SVMs gained a lot of popularity for having nice properties e.g.

1) a convex problem which means a unique solution and a lot of already existing technology can be used

2) the "kernel trick" which enables us to learn in complicated spaces without computing the transformations

3) can be trained online, which makes them great for huge datasets (here the point 2) might not apply - but there exist ways - if someone's interested I can point out some papers)

There is an ongoing craze about deep belief networks developed by Hinton et al. (who is teaching this course) who came up with an algorithm that can train them reasonably well (there exist local optima and such, so it's far from ideal). Some of the reasons they're popular

1) they seem to be winning algorithm for many competitions / datasets, ranging from classification in computer vision to speech recognition and if I'm not mistaken even parsing. They are for example used in the newer Androids.

2) DBNs can be used in an unsupervised mode to _automatically_ learn different representations (features) of the data, which can be then used in subsequent stages of the classification pipeline. This makes them very interesting because while labelled data might be hard to get by, we have a lot of unlabelled datasets thanks to the Internet. As what they can do - see the work by Andrew Ng when they automatically learned a cat detector.

3) DBS are "similar" to biological neural networks, so one might think they have the necessary richness for many interesting AI applications.

nphrk··on Neural Networks for Machine Learning
Well not quite. While SVMs gained a lot of popularity for having nice properties e.g.

  1) a convex problem which means a unique solution and a lot of already existing technology can be used
  2) the "kernel trick" which enables us to learn in complicated spaces without computing the transformations
  3) can be trained online, which makes them great for huge datasets (here the point 2) might not apply - but there exist ways - if someone's interested I can point out some papers)
There is an ongoing craze about deep belief networks developed by Hinton (who is teaching this course) who came up with an algorithm that can train them (there exist local optima and such, so it's far from ideal). Some of the reasons they're popular

  1) They seem to be winning algorithm for many competitions / datasets, ranging from classification in computer vision to speech recognition and if I'm not mistaken even parsing. They are for example used in the newer Androids.
  2) They can be used in an unsupervised mode to _automatically_ learn different representations (features) of the data, which can be then used in subsequent stages of the classification pipeline. This makes them very interesting because while labelled data might be hard to get by, we have a lot of unlaballed datasets thanks to the Internet. As what they can do - see the work by Andrew Ng when they automatically learned a cat detector.
 3) They're "similar" to biological neural networks, so one might think they have the necessary richness for many interesting AI applications.
nphrk··on Rod Johnson joins Typesafe's Board
There's a Coursera course by Martin Odersky going on at the moment (https://class.coursera.org/progfun-2012-001/class/index).
nphrk··on On{X}: The Coolest Thing to Happen to Android. Courtesy of… Microsoft Israel?
I guess you haven't seen the Old Spice commercial [ http://www.youtube.com/watch?v=owGykVbfgUE ].
nphrk··on 20 lines of code that beat A/B testing every time
There are better approaches for tackling this problem (with 0-regret asymptotically). You can take a look at the UCB (Upper Confidence Bound) algorithm, and you can do even more if you assume some continuity, e.g. what is commonly done is to assume that the whole distribution is from a Gaussian Processes. Many interesting ideas in the literature indeed :)
nphrk··on Show HN: Facebook stockvalue (prettified)
Looks nice I must admit :) Are you fitting a quadratic curve? When you have multiple points what do you plan to use - a spline?
nphrk··on Google Summer of Code 2012 Stats - Part 2
No US universities, I guess they can easily get way better paying internships.
nphrk··on Kindergarten Teacher Earns $700,000 by Selling Lesson Plans Online
Unfortunately, even if illegal, there is a way around it. So what some of the teachers where I studied did (one of the eastern European countries) was to send her/his students to visit tutorial classes of the other teacher (for which you pay) and vice versa.
nphrk··on Lenovo refreshes its ThinkPad T, W, L and X
Oh my, why the keyboard? Now I have one less reason to go with a Thinkpad over a MacBook :(.
nphrk··on Stanford profs from DB & Machine Learning class are founding a company Coursera
You have some complaints about the ML class?
nphrk··on Machine Learning on the Cheap and Easy
As I experienced it, Szeliski's book is better as a reference as it covers lots of material (just see the number of citations at the end). I don't think it's an easy read without reading (some of) the cited papers (or having background knowledge).
nphrk··on Machine Learning on the Cheap and Easy
I woundn't consider The Elements of Statistical Learning Theory a (very) basic book. It covers plenty of material in relatively good depth.
nphrk··on Megaupload down, FBI Charges Seven With Online Piracy
Why did they charge the graphic designer and the developers?
nphrk··on Bill Gates Gives Away More Money Than The Entire US Foreign Aid Budget
What is bad about trying to provide "drought-tolerant" seeds to Africa? It's not like GE seeds are gonna ruin Africa, they might very well help fight the hunger problem. I don't understand the general negativity against GE food - if it's tested well, I don't see any reason against it.
nphrk··on Ubuntu 11.10 (Oneiric Ocelot) released
gnome-about says 2.32.1, but I suspect that the Ubuntu version is vanilla
nphrk··on Ubuntu 11.10 (Oneiric Ocelot) released
My experience so far:

* Looks nicer.

* You can't modify the panels. I always had some shortcuts there, now I have to go through the menu.

* You can't even change the default icon theme using the customization app. You have to get gnome-tweak-tool (IIRC).

* ALT+F2 doesn't do anything by default. I guess the key bindings are changed/some are disabled by default.

* It tried to install the new ATI drivers, then miserably failed. Trying to fix it, I purged the old drivers, but it still didn't work. This only caused it to freeze at boot time, so I had to the recovery console to fix it.

* Bottom line: never ever upgrade from an old version. Always do a clean install (or pick up a different distro/OS).

* Note: I'm using Gnome (now not so) classic.

nphrk··on Ask HN: Small product, single founder success stories?
Very nice idea! I have one technical question - do you also use some speech-to-text software, or is it 100% human labor? I believe the utilization of such software (even if it gives crude results) can be of great use to a service like yours.
nphrk··on Fantastic summary of some of the math pertinent to theoretical computer science.
Also, pattern recognition/machine learning.
nphrk··on Students paying to get internships?
Is this Germany (judging from your username) ?
nphrk··on Collect HN: Aprils Fools
You got me there I got to be honest. It took me a while to realize it's April Fools' :).