kappa2N {GeneTS} R Documentation

## Determine the Sample Size from the Degree of Freedom of Correlation Distribution

### Description

The degree of freedom kappa of the sample distribution of the correlation coefficient depends both on the sample size N and the number G of investigated variables, i.e. whether simple or partial correlation coefficients are being considered. For G=2 (simple correlation coefficient) the degree of freedom equals kappa = N-1, whereas for arbitrary G (with G-2 variables eliminated in the partial correlation coefficient) kappa = N-G+1 (see also `dcor0`).

The function `kappa2N` returns the sample size that corresponds to a given degree of freedom kappa, whereas `N2kappa` converts sample size to the corresponding degree of freedom.

### Usage

```kappa2N(kappa, G=2)
N2kappa(N, G=2)
```

### Arguments

 `kappa` degree of freedom `G` number of variables (G=2 corresponds to simple correlation) `N` sample size

### Value

The sample size N corresponding to a given kappa, or the degree of freedom kappa corresponding to a given N.

### Author(s)

Juliane Schaefer (http://www.stat.uni-muenchen.de/~schaefer/) and Korbinian Strimmer (http://www.stat.uni-muenchen.de/~strimmer/).

`dcor0`, `cor0.estimate.kappa`.

### Examples

```# load GeneTS library
library(GeneTS)

# sample sizes corresponding to kappa=7
kappa2N(7)     # simple correlation
kappa2N(7, 40) # partial correlation with 40 variables

# degree of freedom corresponding to N=100
N2kappa(100)
N2kappa(100,40)
```

[Package GeneTS version 2.3 Index]