plotIntLay: Plot Acoustic Survey Data using Different Colored Symbols
In JVAdams/EchoNet2Fish: Estimate Fish Abundance from Acoustic Echoes and Net Catch

Plot acoustic survey data, interval vs. layer, using different colored symbols for data exploration purposes. Place multiple group-specific plots on one page, using the same x- and y-scales.

plotIntLay(
  interval,
  layer,
  group,
  grouporder = sort(unique(group)),
  colorz,
  main = ""
)

`interval`	A numeric vector of intervals along the length of an acoustic transect.
`layer`	A numeric vector of layers from surface to bottom along the vertical water column of an acoustic transect, all values should be <= 0, the same length as `interval`.
`group`	A vector of group identifiers, the same length as `interval`.
`grouporder`	A vector of unique group identifiers, providing the order that each group will be plotted, the same length as `unique(group)`, default `sort(unique(group))`.
`colorz`	A vector of character or numeric colors to use, the same length as `interval`.
`main`	A character scalar of the main title of the plot, default "".