Apply to every unit in the sfc_nxn curve

Usage

# S4 method for sfc_nxn
sfc_apply(p, depth = 1, fun = function(x) x)

Arguments

p: An sfc_nxn object.
depth: An integer between 0 and level-1 of the curve.
fun: A function of which the argument x is a subunit in the curve. The subunit is an sfc_nxn object but only contains the current sub-sequence. The function should return an sfc_seuqence object with the same length as of x. The function can take an optional second argument which the index of the current subunit in the curve.

Details

This function is mainly used to flip subunits on various levels on the curve, thus mainly on the Peano curve and the Meander curve. A depth of 0 corresponds to the complete curve. A depth of 1 corresponds to the nine first-level units, et al.

Currently, sfc_apply() only works on curves with a single base pattern as the seed.

Examples

p = sfc_3x3_peano("I", level = 3)
# flip the global curve
draw_multiple_curves(
    p, 
    sfc_apply(p, 0, sfc_flip_unit),
    nrow = 1
)


# flip all the subunits on depth = 1
draw_multiple_curves(
    p, 
    sfc_apply(p, 1, sfc_flip_unit),
    nrow = 1
)


# flip all the subunits on depth = 2
draw_multiple_curves(
    p, 
    sfc_apply(p, 2, sfc_flip_unit),
    nrow = 1
)


# flip all level-1 patterns on the Peano curve to horizontal
# only works on the lowest subunit, 
p2 = sfc_apply(p, 2, function(x) {
    if(level1_unit_orientation(x) == "vertical") {
        sfc_flip_unit(x)
    } else {
        x
    }
})
# then on depth=1, only flip the unit with odd index
p3 = sfc_apply(p2, 1, function(x, i) {
    if(i %% 2 == 1) {
        sfc_flip_unit(x)
    } else {
        x
    }
})
draw_multiple_curves(p2, p3, nrow = 1)


# flip all level-1 patterns to vertical
p3 = sfc_apply(p, 2, function(x) {
    if(level1_unit_orientation(x) == "horizontal") {
        sfc_flip_unit(x)
    } else {
        x
    }
})
draw_multiple_curves(p, p3, nrow = 1)