• Interactive charts and plots of weekly playcounts
• Charts for only new artists
• Information about extreme weeks

For an example see what it does with my data.

I’m pleased with how it’s turned out.

I also discovered that using a foreign key of an object returned by a Django QuerySet as a dictionary key prompts Django to look the actual data up. I had something like the following:

class WeekData(models.Model):
    artist = models.ForeignKey(Artist)
    plays = models.PositiveIntegerField()
    ..

tracking = defaultdict(int)
for week in WeekData.objects.all():
    tracking[week.artist] += week.plays


The dictionary update was taking ages. Confused, I enabled Mysql’s logging and discovered 25,000 lines of the following..

SELECT `id`, `name` FROM `muncher_artist` WHERE `id` = 22
SELECT `id`, `name` FROM `muncher_artist` WHERE `id` = 23
SELECT `id`, `name` FROM `muncher_artist` WHERE `id` = 24
SELECT `id`, `name` FROM `muncher_artist` WHERE `id` = 25

At which point I realised that using week.artist as the key here looks up the artist every time, meaning 25,000 useless database queries and a really, really slow function. Perhaps I was being too hopeful in my expectation that Django would be clever.

Changing the last line to:

tracking[week.artist_id] += week.plays

sped the function up by a factor of ten and lets me produce images like this in reasonable time:

It’s showing which artists occupy which chart positions as the weeks go by. The dark black line is for Fleet Foxes .. seems I went pretty mad for them :o

Spent some time moving the last.fm charts thing to Python, because Python is tasty, PHP is clumsy, and matplotlib is a superb piece of kit.

Here’s a histogram of the number of tracks I’ve listened to each week for the last few years:

(x is the number of tracks in a week.) I looked at a few friends’ and there seemed quite a split between those roughly following a Gaussian distribution and those following something rather more exponential. I should experiment with different features of matplotlib, maybe narrow those bins a little. I’ve lots of little plans for other graphs and combinations.

Finally, there’s a great little piece about a quirk of the number 1/89 here. Sum the numbers of the Fibonacci Sequence in the following manner:

  .01
  .001
  .0002
  .00003
  .000005
  .0000008
  .00000013
  .000000021
  .0000000034
  .00000000055
  .000000000089
  .0000000000144
        .
    +   .
        .
----------------
  .01123595505...    = 1/89

The link has an outline proof about why it’s true.

Directories only: find . -type d -exec chmod 755 {} \;
Files only : find . -type f -exec chmod 644 {} \;

Life in the Stencil Buffer

One way to create this game using OpenGL is to use a multipass algorithm. Keep the data in the color buffer, one pixel for each grid point. Assume that black (all zeros) is the background color, and the color of a live pixel is nonzero. Initialize by clearing the depth and stencil buffers to zero, set the depth-buffer writemask to zero, and set the depth comparison function so that it passes on not-equal. To iterate, read the image off the screen, enable drawing into the depth buffer, and set the stencil function so that it increments whenever a depth comparison succeeds but leaves the stencil buffer unchanged otherwise. Disable drawing into the color buffer.

Next, draw the image eight times, offset one pixel in each vertical, horizontal, and diagonal direction. When you’re done, the stencil buffer contains a count of the number of live neighbors for each pixel. Enable drawing to the color buffer, set the color to the color for live cells, and set the stencil function to draw only if the value in the stencil buffer is 3 (three live neighbors). In addition, if this drawing occurs, decrement the value in the stencil buffer. Then draw a rectangle covering the image; this paints each cell that has exactly three live neighbors with the “alive” color.

At this point, the stencil buffers contain 0, 1, 2, 4, 5, 6, 7, 8, and the values under the 2’s are correct. The values under 0, 1, 4, 5, 6, 7, and 8 must be cleared to the “dead” color. Set the stencil function to draw whenever the value is not 2, and to zero the stencil values in all cases. Then draw a large polygon of the “dead” color across the entire image. You’re done.

http://www710.univ-lyon1.fr/~jciehl/Public/OpenGL_PG/ch15.html#id5553768

Same process as before – when you first create each kind of chart it’ll take a while to fetch your data, subsequent charts will be created a whole lot faster. Eventually I’ll make a script to purge the data stored for anybody who hasn’t used the program in a couple of months so keep popping back if you get fed up with the waits.

As always comments are welcome. Oh and suggestions for a better name too..

I’ve made it automatically updating, so you only need to add your data once the very first time you visit, and after that it’ll check whether there should be new charts available. Maybe it should only happen a few days into the week – LastFM never get the charts out on time after all..

That and I added a few extra quick links, to 3/6/12/24 months previous. No more ‘wait a month for charts to refresh’ ;-). I should totally see if I can make this into a greasemonkey script..

PHP’s strtotime function is no end of brilliance – strtotime("-6 months") and strtotime("last sunday") are genius conceptions.

Cool, huh?