Extract normalized grid tiles

Unlike grd_tile_template(), which returns a grd() whose elements are the boundaries of the specified tiles with no data attached, grd_tile() returns the actual tile with the data.

grd_tile(grid, level, i, j = NULL)

# S3 method for wk_grd_rct
grd_tile(grid, level, i, j = NULL)

# S3 method for wk_grd_xy
grd_tile(grid, level, i, j = NULL)

Arguments

grid

A grd_xy(), grd_rct(), or other object implementing grd_*() methods.

level

An integer describing the overview level. This is related to the step value by a power of 2 (i.e., a level of 1 indicates a step of 2, a level of 2 indicates a step of 4, etc.).

i, j

1-based index values. i indices correspond to decreasing y values; j indices correspond to increasing x values. Values outside the range 1:nrow|ncol(data) will be censored to NA including 0 and negative values.

Value

A grd_subset()ed version

Examples

grid <- grd_rct(volcano)
plot(grd_tile(grid, 4, 1, 1))

plot(grd_tile(grid, 3, 1, 1), add = TRUE)
plot(grd_tile(grid, 3, 1, 2), add = TRUE)
plot(grd_tile(grid, 3, 2, 1), add = TRUE)
plot(grd_tile(grid, 3, 2, 2), add = TRUE)

grid <- as_grd_xy(grd_tile(grid, 4, 1, 1))
plot(grid, add = TRUE, pch = ".")
plot(grd_tile(grid, 3, 1, 1), add = TRUE, col = "green", pch = ".")
plot(grd_tile(grid, 3, 1, 2), add = TRUE, col = "red", pch = ".")
plot(grd_tile(grid, 3, 2, 1), add = TRUE, col = "blue", pch = ".")
plot(grd_tile(grid, 3, 2, 2), add = TRUE, col = "magenta", pch = ".")