Description Usage Arguments Details Value References Examples

A function to calculate the critical oxygen tension, or the O2 concentration below which uptake rate becomes dependent upon oxygen concentration. It is calculated by both the "broken-stick" regression (BSR) approach, adopted from Yeager and Ultsch (1989), and the segmented regression approach, presented by Muggeo (2003).

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`df` |
data frame or object of class |

`width` |
numeric. Number of rows over which to perform the rolling
regression. Defaults to |

`has.rate` |
logical. Defaults to FALSE. If you already possess a rate~DO dataset, change this to TRUE to process it without performing rolling regressions. |

`plot` |
logical. Defaults to TRUE. |

`parallel` |
logical. Defaults to TRUE. Should parallel processing be used? |

To calculate Pcrit, the function requires data in the form of the rate of
oxygen uptake against dissolved oxygen (DO) concentration. The default data
input is a data frame of DO against time (e.g. `squid.rd`

). The function
performs a rolling regression to determine rates, and matches these against a
rolling mean of the DO data. The function then performs the two
*P[crit]* analyses methods on these data. The width of the
rolling regression is determined by the `width`

argument. In most cases, the
default width (10% of the data length) works well, but this may vary with
data that has abrupt changes in rate, or is particularly noisy.

Alternatively, existing rate~DO data may be used, with the argument `has.rate = "TRUE"`

, in which case the function performs the two
*P[crit]* analyses on these data directly without any
processing.

A list object of class `pcrit`

.

Yeager DP, Ultsch GR (1989) Physiological regulation and conformation: A BASIC program for the determination of critical points. Physiological Zoology 62:888–907. doi: 10.1086/physzool.62.4.30157935

Muggeo V (2008) Segmented: an R package to fit regression models with broken-line relationships. R News 8:20–25.

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januarharianto/respR documentation built on July 30, 2018, 11:18 p.m.

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