Verso notebooks

Install: the extension comes from Verso's Extensions panel — search for MatPlotLibNet.Verso. The charting library itself is an ordinary package: dotnet add package MatPlotLibNet in a project, or #r "nuget: MatPlotLibNet" at the top of a cell.

Verso is an open-source notebook for C#. This extension teaches it to draw this library's charts: a cell that ends on a figure shows the chart instead of a line of type names.

The whole cell

#r "nuget: MatPlotLibNet"

using MatPlotLibNet;

Plt.Create()
   .WithTitle("Revenue")
   .AddSubPlot(1, 1, 1, ax => ax
       .SetXLabel("Quarter")
       .SetYLabel("€M")
       .Plot([1, 2, 3, 4], [12, 18, 15, 22], s => s.Label = "2026")
       .WithLegend())

That is all of it. There is nothing to import from the extension and nothing to call — the chart is the cell's last expression, and it draws inline as SVG.

There is no .Build() in that cell either, on purpose. Plt.Create() hands back a builder, and a notebook shows you whatever the cell ended on, so the builder is what usually arrives. It is drawn like a figure. Plt.Mosaic() is too, and so is a Figure you built earlier and kept in a variable:

var figure = Plt.Create()
                .WithTitle("Revenue, once more")
                .Plot([1, 2, 3, 4], [12, 18, 15, 22])
                .Build();

figure

Every chart this library draws

The extension does not draw anything itself — it hands the library's own SVG to the notebook. So a cell can show any of the 83 chart types, with any of the 148 colormaps, drawn exactly as they are on a server or in a file:

#r "nuget: MatPlotLibNet"

using MatPlotLibNet;
using MatPlotLibNet.Styling;

string[] months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"];
double[] inbound = [120, 145, 138, 170, 162, 191];

Plt.Create()
   .WithTheme(Theme.Dark)
   .WithTitle("Inbound volume")
   .Bar(months, inbound, s => s.Color = Color.FromName("steelblue"))

Candlesticks with indicators, heatmaps, Sankey diagrams, 3-D surfaces and map projections all work the same way: build it, end the cell on it.

How big the picture gets

The chart fills the width of the cell and keeps its proportions — the SVG carries a viewBox, so there is nothing to set.

Height is the one case that needs a decision. A figure taller than the cell can show gets a scroll box; it is not resized. Rewriting the height would re-run the layout, and a chart drawn at a size nobody chose is worse than one you scroll — twelve rows of labels squeezed into the space for four.

Plt.Create()
   .WithSize(800, 2400)          // twelve stacked panels: taller than any cell
   .Plot([1, 2, 3], [4, 5, 6])

Asking for the picture on its own

A cell that asks for image/svg+xml gets the SVG bare, with no HTML around it — useful when you are going to save it or pass it on. The default, text/html, is the one that keeps the links, the accessible name and the responsive width.

When a chart cannot be drawn

The cell says so in words, with the message from the renderer itself. A mosaic whose rows are not the same length, for instance:

MatPlotLibNet could not draw this chart. All rows must have the same length. Row 0 has 2 cells; row 1 has 3. (Parameter 'pattern')

Not a stack trace from inside the charting library. If a cell hands over something that is not a chart at all, the extension says that too, and names what it got.

Notebooks, and the other one

MatPlotLibNet.Notebooks draws the same charts in Polyglot Notebooks and Jupyter. Microsoft has ended the runtime underneath those, so that package stands still at the version it reached, existing notebooks keep working, and new notebook work belongs here — Verso is the open-source notebook built to replace Polyglot.

If what you want is a chart outside a notebook that keeps updating while your program runs, that is MatPlotLibNet.Interactive: it opens a browser window from any program and pushes new data into the chart.

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