traipse (version 0.3.0)

track_grid: Track grid

Description

Computes the cell a track location point falls in on a grid.

Usage

track_grid(x, y, dimension, extent = NULL)

Value

cell index of each input point in the grid specification

Arguments

x

longitude or x

y

latitude or y

dimension

grid size 'nx', 'ny' 2 element vector (ncol, nrow)

extent

grid extent, if not supplied we use the range of the data input

Details

A grid is defined by a 'dimension' ('ncol', 'nrow') and 'extent' ('xmin', 'xmax', 'ymin', 'ymax'). The cell index returned is in 'raster order', this is by top row, left to right and down as per 'rasterImage'. This is aligned with usage in the Github organization 'hypertidy' packages 'vaster' and 'ximage', and is how other raster packages work.

This function doesn't care if the x,y input values are longitude latitude or x, y and it makes no difference at all. No account of movement between points is made.

Examples

dimension <- c(50, 35)
extent <- c(range(trips0$x), range(trips0$y))
cells <- track_grid(trips0$x, trips0$y, dimension = dimension, extent = extent)
plot(extent[1:2], extent[3:4], asp = 1, type = "n")
tab <- tabulate(cells, nbin = prod(dimension))
rasterImage(matrix(1 - (tab/max(tab)), dimension[2L], byrow = TRUE),
extent[1L], extent[3L], extent[2L], extent[4L], interpolate = FALSE)
points(trips0$x, trips0$y, pch = ".", col = "firebrick")