some useful (and relatively uncommon) R tips

http://www.win-vector.com/blog/2009/09/survive-r/

pl/sql function to round down to nearest minute interval

create or replace function nearest_min(dt IN DATE, interval_minutes NUMBER)
return DATE
is
newdate DATE;
BEGIN
newdate := trunc(dt,'HH')+(trunc((dt-trunc(dt,'HH'))*24/(interval_minutes/60)))/(60/interval_minutes)/24;
return newdate;
END;
/

Thanks to http://www.freelists.org/post/oracle-l/Fun-with-SYSDATE-TRUNC-and-rounding,1 for the logic behind the calcuation.

Using Imagemagick to create an animated gif from .png files

With R, I created a series of charts, each representing a sample snapshot at a given time.  I wanted to animate them, and found a wonderful command-line set of utlities called ImageMagick.  I had to jump through quite a few hoops to install ImageMagick on Mac OS X (will post details if/when I get the time), but I'm glad I did.

Here's a sample session where I combine the files into an animate gif:

~/r/tmat>ls
tmat02.png  tmat04.png tmat06.png  tmat08.png tmat10.png  tmat12.png tmat14.png  tmat16.png tmat18.png  tmat20.png
tmat03.png  tmat05.png tmat07.png  tmat09.png tmat11.png  tmat13.png tmat15.png  tmat17.png tmat19.png
~/r/tmat>convert -delay 20 -loop 0 * page_transition.gif

pig on hadoop: count all rows

pt = LOAD 'data'
B = GROUP pt ALL;             
C = FOREACH B GENERATE COUNT(pt);
DUMP C;

actionscript 3: dynamically add attribute to xml element

pf is an XML object, cols is an array of attribute values, and headers is an array of attribute names.

The @[variable name] syntax works the magic.

for(var cn:int=0;cn<cols.length;cn++){
  var col_name:String = headers[cn];
  pf.ROW[rn-1].@[col_name]=cols[cn];
}