14. From C#

C# has no units of measure, so it has the unit-optional mode: a chart takes any IEnumerable<double> (an array, a List<double>, a LINQ query), and each axis a unit as an optional named argument. A stated unit gives the axis what a witness gives it in F#, its title, prefix and the check when two layers meet, at the moment the figure is drawn. The witnesses and their algebra are under Units, the combinators are extension methods on Figure, and the themes, coordinate systems and prefixes are Themes, Coords and Prefixes, all in the Marey.CSharp namespace. The renderers are SvgRenderer, TikzRenderer, PngRenderer and PdfRenderer.

The blocks on this page are not run by the F# session. tests/Marey.CSharp.Tests/Guide.cs holds each of them, runs them, and fails if this page and that file disagree.

§1's dropped ball:

using Marey;
using Marey.CSharp;

double[] tGate = { 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 };
double[] xGate = { 0.051, 0.193, 0.447, 0.779, 1.232, 1.759 };
double[] xErr = tGate.Select(_ => 0.02).ToArray();
double[] tModel = Enumerable.Range(0, 61).Select(i => i * 0.01).ToArray();
double[] xModel = tModel.Select(t => 0.5 * 9.81 * t * t).ToArray();

var fall = Chart.Line(tModel, xModel, xUnit: Units.Second, yUnit: Units.Metre)
    .WithName("½ g t²")
    .Add(Chart.Errorbar(tGate, xGate, xErr, xUnit: Units.Second, yUnit: Units.Metre))
    .WithName("light gate")
    .WithTitle("A dropped ball")
    .WithLegend(LegendPlacement.LegendBest);

fall.Save(SvgRenderer.Render, "fall.svg", 720, 450);
fall.Save(PdfRenderer.Render, "fall.pdf", 720, 450);

§4's Bode plot, with its phase on the right:

double cutoff = 1000.0, zeta = 0.15;
double[] f = Enumerable.Range(0, 241).Select(i => 10.0 * Math.Pow(10.0, i / 60.0)).ToArray();
double[] gain = f.Select(v => 1.0 / Math.Sqrt(Math.Pow(1 - v * v / (cutoff * cutoff), 2) + Math.Pow(2 * zeta * v / cutoff, 2))).ToArray();
double[] phase = f.Select(v => -Math.Atan2(2 * zeta * v / cutoff, 1 - v * v / (cutoff * cutoff))).ToArray();

var phaseSide = Chart.Line(f, phase, xUnit: Units.Hertz, yUnit: Units.Radian)
    .WithName("phase")
    .WithXLog()
    .WithYTicksNamed(new[] { 0.0, -Math.PI / 2, -Math.PI }, new[] { "0", "−π/2", "−π" }, Units.Radian);

var bode = Chart.Line(f, gain, xUnit: Units.Hertz, yUnit: Units.One)
    .WithName("gain")
    .Add(Chart.VLine(cutoff, Units.Hertz))
    .WithXLog()
    .WithYLog()
    .WithRightAxis(phaseSide)
    .WithXLabel("f")
    .WithYLabel("|H|")
    .WithRightYLabel("φ")
    .WithLegend(LegendPlacement.LegendBottomLeft)
    .WithTitle("A second-order low-pass filter, ζ = 0.15");

bode.Save(SvgRenderer.Render, "bode.svg", 720, 450);

A unit known only as text is Units.Parse("V/m"), or Units.Div(Units.Volt, Units.Metre). Category puts categories on the x axis, Figures.Facet draws small multiples, and Grids samples a field from a delegate for §7's marks.