R: Grid a Section in Pressure Space

sectionGrid {oce} | R Documentation

## Grid a Section in Pressure Space

### Description

Grid a section, by interpolating to fixed pressure levels. The `"approx"`, `"boxcar"` and `"lm"` methods are described in the documentation for `ctdDecimate()`, which is used to do this processing.

### Usage

    sectionGrid(
      section,
      p,
      method = "approx",
      trim = TRUE,
      debug = getOption("oceDebug"),
      ...
    )

### Arguments

`section` | A `section` object containing the section to be gridded.
`p` | Optional indication of the pressure levels to which interpolation should be done. If this is not supplied, the pressure levels will be calculated based on the typical spacing in the ctd profiles stored within `section`. If `p="levitus"`, then pressures will be set to be those of the Levitus atlas, given by `standardDepths()`. If `p` is a single numerical value, it is taken as the number of subdivisions to use in a call to `seq()` that has range from 0 to the maximum pressure in `section`. Finally, if a vector numerical values is provided, perhaps. constructed with `seq()` or `standardDepths``(5)` (as in the examples), then it is used as is, after trimming any values that exceed the maximum pressure in the station data stored within `section`.
`method` | The method to use to decimate data within the stations; see `ctdDecimate()`, which is used for the decimation.
`trim` | Logical value indicating whether to trim gridded pressures to the range of the data in `section`.
`debug` | an integer specifying whether debugging information is to be printed during the processing. This is a general parameter that is used by many `oce` functions. Generally, setting `debug=0` turns off the printing, while higher values suggest that more information be printed. If one function calls another, it usually reduces the value of `debug` first, so that a user can often obtain deeper debugging by specifying higher `debug` values.
`...` | Optional arguments to be supplied to `ctdDecimate()`, e.g. `rule` controls extrapolation beyond the observed pressure range, in the case where `method` equals `"approx"`.

### Details

The default `"approx"` method is best for bottle data, the `"boxcar"` is best for ctd data, and the `"lm"` method is probably too slow to recommend for exploratory work, in which it is common to do trials with a variety of `"p"` values.

The stations in the returned value have flags with names that match those of the corresponding stations in the original `section`, but the values of these flags are all set to `NA`. This recognizes that it makes no sense to grid flag values, but that there is merit in initializing a flag system, for possible use in later processing steps.

### Value

A section object that contains stations whose pressure values match identically, and that has all flags set to `NA`.

### Author(s)

Dan Kelley

### See Also

Other things related to section data: `[[,section-method`, `[[<-,section-method`, `as.section()`, `handleFlags,section-method`, `initializeFlagScheme,section-method`, `plot,section-method`, `read.section()`, `section-class`, `sectionAddStation()`, `sectionSmooth()`, `sectionSort()`, `section`, `subset,section-method`, `summary,section-method`

### Examples

    # Gulf Stream
    library(oce)
    data(section)
    GS <- subset(section, 109<=stationId&stationId<=129)
    GSg <- sectionGrid(GS, p=seq(0, 5000, 100))
    plot(GSg, map.xlim=c(-80,-60))
    # Show effects of various depth schemes
    par(mfrow=c(3, 1))
    default <- sectionGrid(GS)
    approxML <- sectionGrid(GS, method="approxML")
    standardDepths5 <- sectionGrid(GS, p=standardDepths(5))
    plot(default, which="temperature", ztype="image", ylim=c(200,0))
    mtext("default sectionGrid()")
    plot(approxML, which="temperature", ztype="image", ylim=c(200,0))
    mtext("sectionGrid(..., method=\"approxML\")")
    plot(standardDepths5, which="temperature", ztype="image", ylim=c(200,0))
    mtext("sectionGrid(..., p=standardDepths(5))")

[Package oce version 1.2-0 Index]