Plots and Drawables

A plot is one panel of a viewer: a title, and a function that is given the run’s data (see The Run’s Data: RunData) and returns what to draw. What it returns is a list of drawables: lines, points, images, numbers or text. Everything between the data and the drawables is yours to compute.

Three ways to write a plot

A function, for most plots. @viz.plot("Title") adds it to the viewer (see The Viewer: Viz):

@viz.plot("Spectral map", weight=3)
def spectral_map(data):
    return [Image(z=data.stack("counts"), y=data.column("hwp_deg"), scale="sqrt",
                  y_label="Plate angle (deg)")]

The decorator returns the function unchanged, so it can still be called directly, for example in a test (see Testing a Viewer).

A Plot subclass, when a plot has to remember something from one refresh to the next, such as a line it is tracking or a running baseline:

from plesty.lib.monitor import Plot

class FineStructure(Plot):
    title = "Fine structure"

    def draw(self, data):
        ...

viz.add_plot(FineStructure())

A widget of your own, when the panel is not a plot at all: a table of the rows, an image browser, a row of readouts. Override Plot.build() and return any Qt widget; draw() is then never called.

The drawables

Drawable	Draws
`Line(x, y, width=, marker=)`	a curve
`Scatter(x, y, size=)`	points
`Image(z, x=, y=, scale=)`	a 2-D array as a colour map, with a colour bar; `scale="sqrt"` makes weak features visible next to strong ones
`Scalar(value, unit=)`	a single number, shown large
`Text(text)`	a line of text in the plot

All are in plesty.lib.monitor. Each also takes label (its name in the legend), color, x_label and y_label. color is a name from the PLESTY palette, one of cyan, violet, mint, amber, rose and blue, never a colour code, so every viewer looks the same.

The values and the style of a drawable are given together, in one call, and a plot can return a different number of drawables from one refresh to the next.

A plot that returns an empty list draws empty axes. That is normal at the start of a run, before the first row is saved.

The same drawables make the figures in an analyzer’s report (see Reports), so a plot on screen and a figure in a report are written the same way.