auxiliary {aws} | R Documentation |

Function `gethani`

determines a bandwidth that leads to, for the specified kernel, a variance reduction for a non-adaptive kernel estimate by a factor of `value`

.
`getvofh`

calculates the sum of location weights for a given bandwidth vector and kernel.
`sofmchi`

precomputes the variance of a non-central chi distribution
with `2*L`

degrees of freedom as a function of the noncentrality parameter for an interval `c(0,to)`

.
Functions `residualVariance`

and `residualSpatialCorr`

are
used in package `fmri`

to calculate variances and spatial correlations from residual objects.

```
gethani(x, y, lkern, value, wght, eps = 0.01)
getvofh(bw, lkern, wght)
sofmchi(L, to = 50, delta = 0.01)
residualVariance(residuals, mask, resscale = 1, compact = FALSE)
residualSpatialCorr(residuals, mask, lags = c(5, 5, 3), compact = FALSE)
```

`x` |
lower bound of search interval |

`y` |
upper bound of search interval |

`lkern` |
code for location kernel |

`value` |
target sum of location weights |

`wght` |
relative size of voxel dimensions |

`eps` |
attempted precision for bandwidth search |

`bw` |
vector of bandwidths, length equal to 1,2 or 3 depending on the dimensionality of the problem. |

`L` |
number of effective coils, |

`to` |
upper interval bound. |

`delta` |
discretization width. |

`residuals` |
array of residuals, if |

`mask` |
mask of active voxel (e.g. brain masks) |

`resscale` |
scale for residuals (residuals may be scaled for optimal integer*2 storage) |

`compact` |
logical, determines if only information for voxel within mask or full for full data cubes is given. |

`lags` |
positive integer vector of length 3, maximum lags for spatial correlations for each coordinate direction to be computed |

These are auxiliary functions not to be used by the user. They are only exported to be available for internal use in packages `fmri`

, `dti`

, `qMRI`

and `adimpro`

.

`gethani`

returns a vector of bandwidths,
`getvofh`

returns the variance reduction that would be obtained with a kernel estimate employing the specified kernel and bandwidth,
`sofmchi`

returns a list with, e.g., components `ncp`

and `s2`

containing vectors of noncentralityparameter values and corresponding variances, respectively, for the specified noncentral Chi distribution,
`residualVariance`

returns a vector (compact==TRUE) or array(compact==FALSE) of voxelwise residual variances,
`residualSpatialCorr`

returns an array of dimension `lags`

containing spatial correlations.

These functions are for internal use only. They are only exported to be available in other packages.

Joerg Polzehl polzehl@wias-berlin.de

[Package *aws* version 2.5-5 Index]