4. Detrending - emboylen/Foxfish_chronology GitHub Wiki
Detrending is the standardization of data - making it easier to interpret and allowing easy comparisons.
As fish get older, their otolith increments get smaller and smaller (see below). Because of this, we have to standarise the data. Standardising the data will allow for individual increments to be compared with each other and other variables.
Detrending is common in dendrochronology and sclerochronology. Often, the data is detrended with either a negative exponential function (due to growth curves, see above), a cubic smoothing spline, and sometimes even a combination of these two methods.
For my honours thesis, I will apply three methods of detrending techniques:
- negative exponential
- cubic smoothing spline
- a combination of these above 2 (called "double detrending") after which I will assess the most appropriate technique via visual (see below) and statistical techniques.
From Wikipedia:
Trend estimation is a statistical technique to aid interpretation of data. When a series of measurements of a process are treated as a time series, trend estimation can be used to make and justify statements about tendencies in the data, by relating the measurements to the times at which they occurred. By using trend estimation it is possible to construct a model which is independent of anything known about the nature of the process of an incompletely understood system (for example, physical, economic, or other system). This model can then be used to describe the behaviour of the observed data.