Figures

gp has no notion of a “current figure” the way R or matplotlib do. A plot reaches the document because you asked gp for it: plothexport("svg", ...) returns the SVG document itself, and the engine turns any cell whose output is an SVG into a figure.

A first plot

plothexport("svg", X = -3, 3, sin(X))

sin(x) on [-3, 3]

print(plothexport(...)) works too; both the quoted value gp prints for a string and the raw printed form are recognised.

Cross-references

Give the cell a label starting with fig- and the figure becomes cross-referenceable, as in Figure 1.

```{gp}
#| label: fig-zeta
#| fig-cap: "Real part of zeta on the critical line"
plothexport("svg", T = 0, 50, real(zeta(1/2 + I*T)))
```

plothexport("svg", T = 0, 50, real(zeta(1/2 + I*T)))

Figure 1: Real part of zeta on the critical line

Several curves at once

plothexport takes a vector of expressions, and the flag 1 joins the points:

plothexport("svg", X = 0.1, 20, [besseljh(0, X), besseljh(1, X)], 1)

Figure 2: Bessel functions \(J_0\) and \(J_1\)

Size

fig-width sets the CSS width of an inline SVG; gp’s own width and height go to plothsizes-aware functions, or as the last arguments of plothexport.

plothexport("svg", X = -3, 3, cos(X))

The same curve at 60% width

How it is emitted

For HTML the SVG goes straight into the page, so it stays sharp at any zoom and there is no file to keep track of. For every other format the SVG is written to the document’s _files directory and referenced as an image, which Quarto copies and cleans up as usual.

Which plotting functions work

The rule is simple: a cell whose output is an SVG document becomes a figure. Every gp function that returns SVG therefore works, and there are three of them:

Function	Draws
`plothexport("svg", X = a, b, expr)`	a function of one variable
`plothrawexport("svg", xs, ys)`	a list of points you computed yourself
`plotexport("svg", w)`	a drawing built with `plotinit` / `plotrecth`

plothrawexport is how you plot data rather than a formula:

xs = vector(40, n, n);
ys = vector(40, n, primepi(n));
plothrawexport("svg", xs, ys)

Figure 3: The first 40 values of \(\pi(n)\)

And plotexport draws a rectangle you composed yourself:

plotinit(0, 480, 300);
plotrecth(0, X = 0, 10, sin(X) * exp(-X/5));
plotexport("svg", 0)

Figure 4: A drawing composed with plotinit and plotrecth

What does not work

ploth, plothraw and plotdraw draw to a screen device, so there is nothing for the engine to capture during a render — use their …export counterparts above.

psploth and psplothraw write a PostScript file (pari.ps by default) rather than returning a string. No browser renders PostScript, so the engine does not pick these up. If you need PostScript, call them, convert the file yourself, and reference the result with ordinary markdown.