Monday, August 16, 2010

Neat new things....

1. sptool is a quick way to compare standards to stellar spectra. Nice, I'd been looking for a tool like that.
2. GNU screen captions are useful especially when working in a screen-within-a-screen environment (who does that, really?)
3. finally got SPLAT to work... turns out I just hadn't reduced my damned data
4. kill -STOP and kill -CONT are really useful ways to pause programs that are sucking up resources if you want to resume them later. Haven't tried this on "real" code yet.

Friday, August 13, 2010

Filled step plots in matplotlib

It's not possible to do a simple filled step plot in matplotlib using default
commands. Workaround:


def steppify(arr,isX=False,interval=0):
"""
Converts an array to double-length for step plotting
"""
if isX and interval==0:
interval = abs(arr[1]-arr[0]) / 2.0
newarr = array(zip(arr-interval,arr+interval)).ravel()
return newarr

plot(xx,yy,linestyle='steps-mid',color='b',linewidth=1.5)
fill_between(steppify(xx[x1:x2],isX=True),
steppify(yy[x1:x2])*0,
steppify(yy[x1:x2]),
facecolor='b',alpha=0.2)

Wednesday, July 28, 2010

Histogram in Google Spreadsheet

It's not easy to make a histogram in google spreadsheets without replicating data. The "countif" function would be great, except it only allows very simple criteria. However, there's a workaround:
=count(Filter('Grades'!V2:V30,'Grades'!V2:V30>0.9))
=count(Filter('Grades'!V2:V30,'Grades'!V2:V30<0.9,'Grades'!V2:V30>0.8))

The Filter() function returns an array, which can be operated on like any other set of cells.

It's still not easy to make a nice-looking histogram, but the output of this process is at least usable.

Friday, July 9, 2010

IDL-to-Python

astrobetter started up an idl-to-python guide on their wiki.