bug in example

[dannygoldstein]

Hi,

When I run example.py, I get:

In [1]: %run example.py
/o/dgold/miniconda/lib/python2.7/site-packages/IPython/parallel.py:13: ShimWarning: The `IPython.parallel` package has been deprecated. You should import from ipyparallel instead.
  "You should import from ipyparallel instead.", ShimWarning)
using 4 engines
importing numpy on engine(s)
importing os on engine(s)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/indirect/o/dgold/gess/example.py in <module>()
     32 
     33 starts = numpy.random.normal(loc=numpy.zeros(dim), scale=1, size=(2*chains,dim))
---> 34 samples, calls = gess.parallel_gess(chains, iters, burnin, thinning, starts, logf, repeats, dview)

/indirect/o/dgold/gess/gess.pyc in parallel_gess(chains, iters, burnin, thinning, starts, logf, repeats, dview)
    120     # do the sampling
    121     for i in xrange(-burnin / repeats, iters / repeats):
--> 122         samples1, calls1 = parallel_tess_update(group1, group2, logf, thinning, repeats, dview)
    123         group1 = samples1[:,repeats / thinning - 1,:]
    124         samples2, calls2 = parallel_tess_update(group2, group1, logf, thinning, repeats, dview)

/indirect/o/dgold/gess/gess.pyc in parallel_tess_update(group1, group2, logf, thinning, repeats, dview)
     73 def parallel_tess_update(group1, group2, logf, thinning, repeats, dview=None):
     74     (n,dim) = group1.shape
---> 75     mu, Sigma, nu = fit_mvstud.fit_mvstud(group2)
     76     if nu == numpy.Inf:
     77         nu = 1e6

/indirect/o/dgold/gess/fit_mvstud.pyc in fit_mvstud(data, tolerance)
     35         # update nu
     36         last_nu = nu
---> 37         nu = opt_nu(delta_iobs, nu)
     38         if nu == numpy.inf:
     39             return mu.T[0], Sigma, nu

/indirect/o/dgold/gess/fit_mvstud.pyc in opt_nu(delta_iobs, nu)
     13             nu = numpy.inf
     14         else:
---> 15             nu = optimize.brentq(func0, 1e-6, 1e6)
     16         return nu
     17 

/o/dgold/miniconda/lib/python2.7/site-packages/scipy/optimize/zeros.pyc in brentq(f, a, b, args, xtol, rtol, maxiter, full_output, disp)
    436     if rtol < _rtol:
    437         raise ValueError("rtol too small (%g < %g)" % (rtol, _rtol))
--> 438     r = _zeros._brentq(f,a,b,xtol,rtol,maxiter,args,full_output,disp)
    439     return results_c(full_output, r)
    440 

ValueError: f(a) and f(b) must have different signs