interpolate_section: Interpolate x-y-z data for oceanographic section plots
In MikkoVihtakari/WaterMass: Helpers for the Analysis of Oceanographic Data

Description Usage Arguments Details Value Author(s)

Wrapper function which interpolates 3D data. Designed for oceanographic section plots.

interpolate_section(
  df = NULL,
  x,
  y,
  z,
  method = "linear",
  format = "ggplot",
  nx = 100,
  ny = 100,
  scale_distances = FALSE,
  log_y = FALSE,
  extrapolate = FALSE,
  na.rm = TRUE,
  return_df_names = FALSE
)

`df`	data frame. Can be `NULL` if `x, y, z` are given as numeric vectors
`x, y, z`	coordinates as numeric vectors, if `df = NULL`. Otherwise characters specifying the column names of the coodrinates in `df`. The interpolation will be done as f(x, y) ~ z
`method`	Character specifying the interpolation method. Options: "linear", "spline", "mba", and "idw"
`format`	Character specifying the output format. Options: "ggplot" (for plotting with ggplot2), "image" (for plotting with the `image` function) or "wide" for exporting as a wide data frame.
`nx, ny`	Integer giving the dimensions for the output
`scale_distances`	Logical indicating whether `x` and `y` should be scaled to equal distances. May be useful when interpolating variables that have different units or distances.
`log_y`	logical indicating whether y axis should be interpolated using `log10(y + 1)` scale.
`extrapolate`	logical indicating whether the interpolation function should be allowed to extrapolate beyond initial data.
`na.rm`	logical indicating whether rows containing NA values should be omited from `df` or `x, y, z`. NA values are not permitted in most of the interpolation methods. See `sectionGrid` for one way of interpolating NA values away from the input dataset.
`return_df_names`	logical indicating whether the original column names should be returned instead of x, y, and z if `df != NULL`

This is a wrapper function which uses existing interpolation solutions. Following interpolation methods have been implemented:

"linear" for linear interpolation using the interp function with linear = TRUE.
"spline" for spline interpolation using the interp function with linear = FALSE.
"mba" for multilevel B-spline interpolation using the mba.surf function. Appears to produce the best looking results. Recommended.
"idw" for inverse distance weighted interpolation using the idw function. This function was originally developed for spatial data where x- and y axes are given in the same units and have similar effect on the result. While it would, no doubt, be possible to account section design in the model specification, this has not been done in the interpolate_section function. Therefore, using this option is not recommended.