# Second E step of the AECM algorithm when fitting a mixture of PPCA models.

### Description

Internal function required for fitting a mixture of PPCA models.

### Usage

1 | ```
estep2(Y, Tau, Pi, mu, W, Sig, g, p, reset)
``` |

### Arguments

`Y` |
A N x p data matrix. |

`Tau` |
An N x g matrix of posterior group membership probabilities. |

`Pi` |
A g vector of group probabilities. |

`mu` |
A p x g matrix containing the mean for each group. |

`W` |
An p x q x g array of loadings for each group. |

`Sig` |
A scalar; the error covariance. |

`g` |
The number of groups currently being fitted. |

`p` |
Number of spectral bins in the NMR spectra. |

`reset` |
Logical indicating computational instability. |

### Details

Second E step of the AECM algorithm when fitting a mixture of PPCA models. An internal function.

### Value

A list containing

`Tau` |
The N x G matrix of posterior group membership probablities. |

`logTau` |
An N x G matrix of the log of the numerator of posterior group membership probablities. |

`reset` |
Logical indicating computational instability. |

### Note

An internal function.

### Author(s)

Nyamundanda Gift, Isobel Claire Gormley and Lorraine Brennan

### References

Nyamundanda, G., Gormley, I.C. and Brennan, L. (2010) Probabilistic principal components analysis for metabolomic data. Technical report. University College Dublin, Ireland.

### See Also

`mppca.metabol`