Legend Wrap

When the legend contains many items, it automatically wraps to prevent overlap - up to 15 rows for vertical legends and 5 columns for horizontal ones.

%useLatestDescriptors
%use lets-plot

LetsPlot.getInfo()

Lets-Plot Kotlin API v.4.12.0. Frontend: Notebook with dynamically loaded JS. Lets-Plot JS v.4.8.1.
Outputs: Web (HTML+JS), Kotlin Notebook (Swing), Static SVG (hidden)

// Prepare a dataset

import kotlin.math.roundToInt
import kotlin.random.Random

private fun Double.to255(): Int = (coerceIn(0.0, 1.0) * 255.0).roundToInt()

fun hlsToRgb(h: Double, l: Double, s: Double): Triple<Int, Int, Int> {
    fun hue2rgb(p: Double, q: Double, t0: Double): Double {
        var t = t0
        if (t < 0) t += 1.0
        if (t > 1) t -= 1.0
        return when {
            t < 1.0 / 6 -> p + (q - p) * 6 * t
            t < 1.0 / 2 -> q
            t < 2.0 / 3 -> p + (q - p) * (2.0 / 3 - t) * 6
            else -> p
        }
    }
    val q = if (l < 0.5) l * (1 + s) else l + s - l * s
    val p = 2 * l - q
    val r = hue2rgb(p, q, h + 1.0 / 3)
    val g = hue2rgb(p, q, h)
    val b = hue2rgb(p, q, h - 1.0 / 3)
    return Triple(r.to255(), g.to255(), b.to255())
}


fun distinctPalette(n: Int, s: Double = 0.72, l: Double = 0.53): List<String> =
    List(n) { i ->
        val (r, g, b) = hlsToRgb(i.toDouble() / n, l, s)
        "#%02X%02X%02X".format(r, g, b)
    }
    
val nCats = 36
val ptsPerCat = 13
val cats = (1..nCats).map { i -> "C%02d".format(i) }
val cols = 6

val rnd = Random(42)
data class Pt(val x: Double, val y: Double, val cat: String)

val points: List<Pt> = cats.flatMapIndexed { i, c ->
    List(ptsPerCat) {
        val x = (i % cols) + rnd.nextDouble(-0.4, 0.4)
        val y = (i / cols) + rnd.nextDouble(-0.4, 0.4)
        Pt(x, y, c)
    }
}

val xs = points.map { it.x }
val ys = points.map { it.y }
val catCol = points.map { it.cat }

val data = mapOf("x" to xs, "y" to ys, "cat" to catCol)

val palette = distinctPalette(nCats)

val base =
    letsPlot(data) { x = "x"; y = "y"; color = "cat" } +
        geomPoint(size = 3.0, alpha = 0.9) +
        scaleColorManual(values = palette, name = "Categories ($nCats)") +
        ggsize(800, 460)

// The default legend layout (vertical)

base

// The horizontal case

base + theme().legendPositionBottom()

// You can still adjust the number of legend rows or columns manually.

base +
    theme().legendPositionBottom() +
    guides(
        color = guideLegend(
            ncol = 10, 
            byRow = true)
    )