def _ma_transparams(params):
 newparams = ((1 - np.exp((- params))) / (1 + np.exp((- params)))).copy()
 tmp = ((1 - np.exp((- params))) / (1 + np.exp((- params)))).copy()
 for j in range(1, len(params)):
  b = newparams[j]
  for kiter in range(j):
   tmp[kiter] += (b * newparams[((j - kiter) - 1)])
  newparams[:j] = tmp[:j]
 return newparams

def _ma_transparams ( params ) : newparams = ( ( 1 - np . exp ( ( - params ) ) ) / ( 1 + np . exp ( ( - params ) ) ) ) . copy ( ) tmp = ( ( 1 - np . exp ( ( - params ) ) ) / ( 1 + np . exp ( ( - params ) ) ) ) . copy ( ) for j in range ( 1 , len ( params ) ) : b = newparams [ j ] for kiter in range ( j ) : tmp [ kiter ] += ( b * newparams [ ( ( j - kiter ) - 1 ) ] ) newparams [ : j ] = tmp [ : j ] return newparams
transforms params to induce stationarity/invertability .