macro

metrop x vx;
 iter k;
 scale sx.

mcolumn vx z1 u1 xx f
mconstant x xc xn i k sx prob
default k=1000 sx=1

let xc=x
rand k z1
rand k u1;
  uniform 0 1.

do i=1:k
  let xn=xc+z1(i)*sx
  copy xc xn xx
  %logpost xx f
  let prob=exp(f(2)-f(1))
  if u1(i)<prob
    let xc=xn
  endif
  let vx(i)=xc
  if i/10=round(i/10)
    print i
  endif
enddo


endmacro