# R Language
df = read.delim('07_table.dat', header=TRUE)
for(snippet in levels(df$snippet)) 
	df[df$snippet == snippet, "z.duration"] = scale(df[df$snippet == snippet, "duration"])


# Python with NumPy, SciPy and Pandas
import pandas
import scipy.stats as stats

df = pandas.read_csv('07_table.dat', delimiter='\t')

## Magic!
df['zduration'] = df.groupby('snippet', sort=False).transform(stats.zscore).duration