Description Usage Arguments Details Value Note Author(s) References See Also Examples

Computes the Lomb-Scargle periodogram for a time series with irregular (or regular) sampling intervals. Allows selecting a frequency range to be inspected, as well as the spacing of frequencies scanned.

1 2 |

`x` |
The data to be analysed. x can be either a two-column numerical dataframe or matrix, with sampling times in columnn 1 and measurements in column 2, a single numerical vector containing measurements, or a single vector |

`times` |
If x is a single vector, times can be provided as a numerical vector of equal length containing sampling times. If x is a vector and times is NULL, the data are assumed to be equally sampled and times is set to 1:length(x). |

`from` |
The starting frequency (or period, depending on type) to begin scanning for periodic components. |

`to` |
The highest frequency (or period, depending on type) to scan. |

`type` |
Either “frequency” (the default) or “period”. Determines the type of the periodogram x-axis. |

`ofac` |
The oversampling factor. Must be an integer>=1. Larger values of ofac lead to finer scanning of frequencies but may be time-consuming for large datasets and/or large frequency ranges (from...to). |

`alpha` |
The significance level. The periodogram plot shows a horizontal dashed line. Periodogram peaks exceeding this line can be considered significant at alpha. Defaults to 0.01. Only used if plot=TRUE. |

`plot` |
Logical. If plot=TRUE the periodogram is plotted. |

`...` |
Further graphical parameters affecting the periodogram plot. |

The p-value for the significance of the largest peak in the periodogram is computed from the exponential distribution, as outlined in Press et al. (1994), see below. For a more robust - but potentially time-consuming estimation of p-values see `randlsp`

.

Significance levels in both lsp and `randlsp`

increase with the number of frequencies inspected. Therefore, if the frequency-range of interest can be narrowed down *a priori*, use arguments “from” and “to” to do so.

A named list with the following components:

`scanned` |
A vector containing the frequencies/periods scanned. |

`power` |
A vector containing the normalised power corresponding to scanned frequencies/periods. |

`data` |
Names of the data vectors analysed. |

`n` |
The length of the data vector. |

`type` |
The periodogram type used, either "frequency" or "period". |

`ofac` |
The oversampling factor used. |

`n.out` |
The length of the output (powers). This can be >n if ofac >1. |

`alpha` |
The false alarm probability used. |

`sig.level` |
Powers > sig.level can be considered significant peaks at p=alpha. |

`peak` |
The maximum power in the frequency/period interval inspected. |

`peak.at` |
The frequency/period at which the maximum peak occurred. |

`p.value` |
The probability that the maximum peak occurred by chance. |

For a description of the properties of the Lomb-Scargle Periodogram, its computation and comparsion with other methods see Ruf, T. (1999). Function lsp uses the algorithm given by Press et al (1994). The Lomb-Scargle Periodogram was originaly proposed by Lomb N.R. (1976) and furher extended by Scargle J.D. (1982).

Thomas Ruf thomas.ruf@vetmeduni.ac.at based on code by Press et al (1994).

Lomb N.R. (1976) Least-squares frequency analysis of unequally spaced data. *Astrophysics and Space Science* **39**:447–462

Press W.H., Teukolsky S.A., Vetterling S.T., Flannery, B.P. (1994) *Numerical recipes in C: the art of scientific computing.*2nd edition. Cambridge University Press, Cambridge, 994pp.

Ruf, T. (1999) The Lomb-Scargle Periodogram in Biological Rhythm Research: Analysis of Incomplete and Unequally Spaced Time-Series. *Biological Rhythm Research* **30**: 178–201.

Scargle J.D. (1982) Studies in astronomical time series. II. Statistical aspects of spectral analysis of unevenly spaced data. *The Astrophysical Journal* **302**: 757–763.

1 2 3 4 5 6 7 8 9 |

Embedding an R snippet on your website

Add the following code to your website.

For more information on customizing the embed code, read Embedding Snippets.