[SciPy-User] broadened step functions

[Christian K.]

Hi,

can you think of a faster way to evaluate a broadened step function, 
i.e. the convolution of a heavyside step function with e.g. a Lorentz 
function, than this here?

def lbstep(x,amp,pos,sigma,sigmap=100.0):
     dx = x[-1]-x[0]
     up = x[-1]+5*dx
     lo = x[0]-5*dx
     f = amp/N.pi
     xp = N.linspace(lo,up,1000.0)[:,N.newaxis]
     s2 = N.power(sigma,2)
     i = trapz(sigma/(N.power(x-xp,2)+s2)/ \
         (1+N.exp(-sigmap*(xp-pos))), xp, axis=0)
     return f*i

Speed depends naturally on the length of x and xp and the accuracy also 
on the upper and lower integration limits.

Thanks for any idea, Christian