exponentialFilter <-
function (bDat, alpha=.5,meanInnovation=0) {
  ## Assumes that the est field of bData contains an array of
  ## estimates for all the time points so far.  This function
  ## estimates the next row.
  icycle <- lastEstimate(bDat)
  obs <- bDat@obs[,,icycle+1]
  if (icycle == 0) {
    return (obs)
  }
  est <- bDat@est[,,icycle]
  alpha*obs + (1-alpha)*sweep(est,2,meanInnovation,"+")
}


meanPlusPolicy <-
function (estimate,lead=.25) {
  mest <- apply(estimate,1,mean)
  mest+lead
}