gsw {gsw} | R Documentation

## R implementation of Thermodynamic Equation Of Seawater - 2010 (TEOS-10)

### Description

Provides an R interface to the TEOS-10 / GSW (Gibbs Sea Water) library, partly for use by the `oce` package (see http://dankelley.github.io/oce) and partly for general use. It is assumed that users are familiar with the science and methodology of GSW, and that the package vignette (obtained by typing `vignette("gsw")` in an R window) provides enough orientation to get users started with the `gsw` functions.

### Details

`gsw` was developed using open-source methodologies, on the GitHub site (https://github.com/TEOS-10/GSW-R), which is part of a set of sites dedicated to GSW formulations in various languages.

The `gsw` system is to link R functions with the C version of the TEOS-10 library. The R function names are chosen to match those of the Matlab version of GSW, and the function arguments also match with one exception: in `gsw`, longitude and latitude are indicated with their full names, whereas in Matlab they are indicated with `long` and `lat`; since R permits abbreviated function arguments, the shortened names can be used in `gsw` as well.

The documentation for the `gsw` functions focuses mainly on the arguments and return values, relying on links to the TEOS-10 webpages for details.

See http://www.teos-10.org/pubs/gsw/html/gsw_contents.html for a list of the TEOS-10 functions and http://teos-10.github.io/GSW-R/documentation.html for a list of the functions implemented in the present package.

Each function is tested during the building of the package, which means that results are guaranteed to match those of the equivalent Matlab functions to at least 8 digits.

A significant difference from the Matlab case is in the inspection of the dimensions of arguments. The Matlab library has rules for expanding some arguments to match others. For example, if Practical Salinity is a matrix and pressure is a single value, then that single pressure is used throughout a calculation of Absolute Salinity. This convenience is only partly mimicked in the present package. Since the underlying C code works on vectors, the R functions in `gsw` start by transforming the arguments accordingly. This involves using `rep` on each argument to get something with length matching the first argument, and, after the computation is complete, converting the return value into a matrix, if the first argument was a matrix. There are some exceptions to this, however. For example, `gsw_SA_from_SP` and similar functions can handle the case in which the `SA` argument is a matrix and `longitude` and `latitude` are vectors sized to match. This can be handy with gridded datasets. However, the careful analyst will probably prefer to avoid this and other conveniences, supplying properly-matched arguments from the outset.

[Package gsw version 1.0-5 Index]