Lines

val mpgDf =
    DataFrame.readCSV("https://raw.githubusercontent.com/JetBrains/lets-plot-kotlin/master/docs/examples/data/mpg.csv")
mpgDf.head()

untitled	manufacturer	model	displ	year	cyl	trans	drv	cty	hwy	fl	class
1	audi	a4	18,0	1999	4	auto(l5)	f	18	29	p	compact
2	audi	a4	18,0	1999	4	manual(m5)	f	21	29	p	compact
3	audi	a4	2,0	2008	4	manual(m6)	f	20	31	p	compact
4	audi	a4	2,0	2008	4	auto(av)	f	21	30	p	compact
5	audi	a4	28,0	1999	6	auto(l5)	f	16	26	p	compact

Vertical, horizontal and oblique lines

val ctyMedian = mpgDf.median { cty }
val hwyMedian = mpgDf.median { hwy }

val medianColor = Color.hex("#756bb1")
mpgDf.plot {
    points {
        x(cty)
        y(hwy)
    }
    vLine {
        xIntercept.constant(ctyMedian)
        color = medianColor
        type = LineType.DASHED
    }
    hLine {
        yIntercept.constant(hwyMedian)
        color = medianColor
        type = LineType.DASHED
    }
    smoothLine("cty", "hwy", method = SmoothMethod.Linear()) {
        color = Color.hex("#de2d26")
    }
}

Broken Lines

fun generateParabolicDataMap(n: Int = 25, a: Double = 1.0): Map<String, List<Double>> {
    val rand = java.util.Random(42)
    val x = List(2 * n + 1) { i -> a * (i - n).toDouble() / n }
    val y = x.map { i -> i * i + rand.nextGaussian() }
    return mapOf("x" to x, "y" to y)
}

val pDataMap = generateParabolicDataMap(a = 3.0)
val xSrc = column<Double>("x")
val ySrc = column<Double>("y")

plot(pDataMap) {
    line {
        x(xSrc)
        y(ySrc)
    }
}

plot(pDataMap) {
    path {
        x(xSrc)
        y(ySrc)
    }
}

plot(pDataMap) {
    step {
        x(xSrc)
        y(ySrc)
    }
}

And what is the difference between line and path?

Let's have a look at the following example:

fun generateArchimedeanDataMap(n: Int = 25, k: Double = 1.0, a: Double = 1.0): Map<String, List<Double>> {
    val phi = List(n) { i -> 2.0 * PI * k * i.toDouble() / (n - 1) }
    val r = phi.map { angle -> (a * angle) / (2.0 * PI) }
    val x = (r zip phi).map { p -> p.first * cos(p.second) }
    val y = (r zip phi).map { p -> p.first * sin(p.second) }
    return mapOf("x" to x, "y" to y)
}

val aDataMap = generateArchimedeanDataMap(n = 200, k = 2.0)

val linePlot = plot(aDataMap) {
    line {
        x(xSrc)
        y(ySrc)
    }
    layout.title = "Line Plot"
}

val pathPlot = plot(aDataMap) {
    path {
        x(xSrc)
        y(ySrc)
    }
    layout.title = "Path Plot"
}

val segments = plot(generateArchimedeanDataMap(n = 50)) {
    segments {
        xBegin(xSrc)
        yBegin(ySrc)
        xEnd.constant(0.0)
        yEnd.constant(0.0)
    }
}
plotBunch {
    add(linePlot, 0, 0, 350, 300)
    add(pathPlot, 350, 0, 350, 300)
    add(segments, 0, 300, 700, 300)
}

Last modified: 28 November 2023