Contour

from std.math import exp

from dataviz import contour
from dataviz import save

def main() raises:
    # Illustrative elevation model: two ridges separated by a saddle.
    var z = List[List[Float64]]()
    for r in range(48):
        var row = List[Float64]()
        for c in range(64):
            var x = (Float64(c) - 31.5) / 10.0
            var y = (Float64(r) - 23.5) / 10.0
            var west = exp(-((x + 1.5) * (x + 1.5) + y * y))
            var east = exp(
                -((x - 1.4) * (x - 1.4) + (y - 0.4) * (y - 0.4))
            )
            var saddle = exp(-(x * x / 2.2 + (y + 0.2) * (y + 0.2)))
            row.append(420.0 + 980.0 * west + 760.0 * east - 260.0 * saddle)
        z.append(row^)

    var c = contour(
        z,
        level_count=11,
        title="Illustrative Mountain Elevation Contours (m)",
        x_title="East-west grid cell",
        y_title="North-south grid cell",
    )
    save(c, "docs/src/examples/out_contour.svg")