Isolines Over a Filled Field

from std.math import cos, sin

from dataviz.chart import AnyChart
from dataviz import Plot, save_layers
from dataviz.core.theme import Theme
from dataviz.core.colormaps import viridis


def main() raises:
    # A deterministic scatter of samples over a smooth field.
    var x = List[Float64]()
    var y = List[Float64]()
    var z = List[Float64]()
    var seed = 12345
    for _ in range(120):
        seed = (seed * 1103515245 + 12345) % 2147483648
        var px = Float64(seed % 1000) / 100.0
        seed = (seed * 1103515245 + 12345) % 2147483648
        var py = Float64(seed % 1000) / 100.0
        x.append(px)
        y.append(py)
        z.append(sin(px) * cos(py))

    var field = (
        Plot()
        .mark_tricontourf(levels=9)
        .encode_tricontour(x=x, y=y, z=z)
        .theme(Theme(color_ramp=viridis()))
        .labels(title="Sampled field, filled bands with isolines")
        .size(640, 440)
    )
    var isolines = (
        Plot()
        .mark_tricontour(levels=9)
        .encode_tricontour(x=x, y=y, z=z)
        .theme(Theme(color_ramp=viridis(), line_width=1.0))
        .size(640, 440)
    )

    var plots: List[AnyChart] = [AnyChart(field), AnyChart(isolines)]
    save_layers(plots, "docs/src/examples/out_isolines_over_a_field.svg")