# here is a little roller coaster
# designed with XFig and exported as a table
# only the y-values are relevant as the x-values are uniformly spaced
# This is really only an approximation
# 
tab fraw coaster.tab
y(x)=fraw(x)*.01
dy(x)=(y(x+h)-y(x))/h
par h=.1
x'=v
v'=a*dy(x)-g(x)*v
yy=(63-y(x))/48
xx=x/50
g(x)=fmax/(1+exp(-(x-xt)/xs))
par a=1,fmax=.35,xt=38,xs=1
done