# A step in the SFA2 algorithm.

### Description

!!! Do not use this function directly, use sfaStep instead !!!

### Usage

1 |

### Arguments

`sfaList` |
A list that contains all information about the handled sfa-structure |

`arg` |
Input data, each column a different variable |

`step` |
Specifies the current SFA step. Must be given in the right sequence:
for SFA1 objects: "preprocessing", "sfa" |

`method` |
Method to be used: For |

### Value

list `sfaList`

taken from the input, with new information added to this list.
Among the new items are:

`avg0` |
mean vector in input space |

`avg1` |
mean vector in expanded space |

`W0` |
(ppRange x ppRange)-matrix, the whitening matrix for the input data |

`C` |
covariance matrix of the time-diff of expanded and sphered data |

`SF` |
(sfaRange x sfaRange)-matrix with rows which contain the directions in expanded space with slow signals. The rows are sorted acc. to increasing eigenvalues of C |

### See Also

`sfaStep`

`sfa2Create`

`sfa1Step`