PWLINT: Piecewise Linear Integration

Return positive and negative areas, assuming a piecewise linear function

PWLINT.m
Calculate the positive and negative area under a curve
using trapezoids, assuming a piecewise linear function

Requires insertrows:
http://www.mathworks.com/matlabcentral/fileexchange/9984

Inspired by this thread:
http://www.mathworks.com/matlabcentral/newsreader/view_thread/252131

Usage:
[Apos, Aneg, Anet] = pwlint(x,y)
x: vector of independent variable
y: vector of dependent variable
Apos: area between y=0 and positive y values
Aneg: area between y=0 and negative y values
Anet: Apos+Aneg; equal to trapz(x,y)

See also TRAPZ, SUM