To make a density map from a 2D set of data, the first step is to compute values for the third dimension. (Gnuplot has no facilities for computing these values automatically.) The simplest way is to make a 2D histogram; the plot is divided in small 2D regions, and the z-values are proportional to the number of points inside these regions. The following Python script will make an histogram from a time series of two dihedral angles.
Last week, Diaspora — the OSS privacy-respecting social network — released a “pre-alpha developer preview” of their source code. I took a look out it, mostly out of curiosity, and was struck by numerous severe security errors. I then spent the next day digging through their code locally and trying to get in touch with the team to address them, privately. In the course of this, I mentioned obliquely that the errors existed on Hacker News, and subsequently was interviewed by The Register and got quoted in a couple of hundred places.
This routine will take an 8 bit integer that corresponds to the numerator of a fraction whose denominator is 256 and find its arctangent. So the input ranges from 0 to 255 which corresponds to 0 to 255/256 = 0.996 . The output for an arctangent routine that returns a floating point number would be from 0 (atan(0)) to 0.783 (atan(255/256)) radians; or if you prefer, 0 to 44.89 degrees. However, this routine scales the output so that pi/4 radians (or 45 degrees) corresponds to 256. So for the input range of 0 to 255 you get an output of 0 to 255 ( atan(255/256) * 256 / (pi/4) is about 255). It's probably a little more interesting to see an intermediate data point or two:
In this excerpt, one of a series from Java Network Programming, 3rd Edition, Elliotte Rusty Harold demonstrates Java's handling of URLs, URIs, proxy servers, password protection, and HTTP GET.
Every field comes up with its own jargon, and oftentimes subgroups within a field come up with their own specific words or phrases (those of you familiar with Microsoft Canada’s Developer and Platform Evangelism Team know that we have our own term for “broken”, named after one of our teammates who is notorious for killing all sorts of tech gear).
A question recently posted on Stack Overflow asked for people to submit programming terms that they or their team have coined and have come into regular use in their own circles. I took a number of the submissions and compiled them into the alphabetically ordered list below for your education and entertainment.
S. Ahmad, A. Battle, Z. Malkani, and S. Kamvar. Proceedings of the 24th annual ACM symposium on User interface software and technology, page 53--64. New York, NY, USA, ACM, (2011)