# okay - here is how to do the correlations part
# for probelm 1 chapt 2 using XPP
# step 1 do the simulation ch2ex1.ode
# pull up the data browser
# click on "Table" and save "R" in a file R.tab, with xlo=0,xhi=1000
# Make a table for "stim" in s.tab as well with xlo=0,xhi=1000
# run this ODE file
#
# reads in the two columns
table r R.tab
table s s.tab
# periodizes them
rr(x)=r(mod(x,1000))
ss(x)=s(mod(x,1000))
# set up an iteration
@ meth=discrete,total=25
# set up some plots
@ nplots=2,xp=k,yp=q,yp2=dval
@ xlo=-1,xhi=25,ylo=-1,yhi=.5
#
init k=-1,q=0
# here is the iteration
k'= k+1
# here is the cross correlation divided by sig^2
q'= sum(0,1000)of(ss(i')*rr(i'+k))/10000
# here is original function
d(t)=-cos(2*pi*(t-20)/140)*exp(-t/60)
# and its plot
aux dval=d(k*10)
done