Plots

Video: Plots in the sheet format

There are three ways to draw: the plot line of the sheet format, the Calcpad $Plot and $Map commands, and Python blocks, which are covered in Python blocks. All three can sit in the same sheet.

Charts that are not drawn from a function, such as a pie chart, a Gantt chart, a Sankey diagram or a bar chart of values you type, are diagrams written as text. See Diagrams for a gallery of every kind, and the Plots and diagrams group of the samples.

The `plot` line

L: 6
w: 12
M(x): w * x * (L - x) / 2
plot M(x) for x in 0..L

The line is plot expression for variable in from..to. It becomes $Plot{ M(x) @ x = 0 : L }. The expression can be a function you defined, or any expression of the variable:

>> #rad
plot sin(x), cos(x) for x in 0..2*π

Several expressions, separated by commas, are drawn together, each in its own colour. An optional y = before the expressions is dropped (plot y = f(x) for x in 0..10). A malformed plot line is reported on its line in the report and in the editor.

A legend

Give a curve a name with as "name" after its expression, and the plot gets a legend in its top right corner: a colour swatch and the name of each curve.

>> #rad
plot sin(x) as "sine", cos(x) as "cosine" for x in 0..2*π

A curve without a name is listed by its expression, and a plot where no curve has a name has no legend, as before. A name cannot contain quotes, &, |, @ or braces. The legend is part of the SVG, so it is in the printout and the PDF and in the Word picture; in Excel the names are the series names of the chart. In Calcpad text the name follows the expression in double quotes, $Plot{sin(x) "sine" & cos(x) "cosine" @ x = 0 : 2*π} (this is not in CalcpadCE).

The plot is an SVG drawing. It is sharp at any zoom, it prints well, and its data is exported to Excel as a native chart.

Radians, not degrees

Angles are in degrees by default. sin(x) over 0..2*π is then the sine of the first six degrees, which is a nearly flat line. Put >> #rad in the sheet before the plot, as above, or plot over degrees (0..360).

Plotting a function with units

The plotted variable must be a plain number. If L is 6 m, then for x in 0..L stops with Inconsistent units. Give the variable the unit inside the expression instead:

L: 6 m
w: 12 kN/m
M(x): w * x * (L - x) / 2
plot M(x * 1 m) for x in 0..6

The axes are labelled with the variable names, and the end points of the curve are marked with their values.

Other kinds of plot: `$Plot` and `$Map`

A sheet reaches the rest of the plotting commands through >> lines.

>> #rad
>> $Plot{cos(t) | sin(t) @ t = 0 : 2*π}
>> $Plot{cos(t) | sin(t) & 2*cos(t) | 2*sin(t) @ t = 0 : 2*π}
>> $Map{x*y @ x = -1 : 1 & y = -1 : 1}

Form	Draws
`$Plot{y(x) @ x = a : b}`	A function of one variable.
`$Plot{y1(x) & y2(x) @ x = a : b}`	Several functions on one plot.
`$Plot{y1(x) "name 1" & y2(x) "name 2" @ x = a : b}`	The same, with a legend.
`$Plot{x(t) \| y(t) @ t = a : b}`	A parametric curve.
`$Plot{x1(t) \| y1(t) & x2(t) \| y2(t) @ t = a : b}`	Several parametric curves.
`$Map{f(x; y) @ x = a : b & y = c : d}`	A colour map of a surface.

$Plot must be the first thing on its line. Anything after the closing brace is ignored. Plotting supports real numbers only.

Size and style

Set these by assigning them on a line of their own (in a sheet, a >> line), before the plot:

L: 6
w: 12
M(x): w * x * (L - x) / 2
>> PlotWidth = 600
>> PlotHeight = 300
plot M(x) for x in 0..L

Setting	Meaning
`PlotWidth`, `PlotHeight`	Size of the plot area in pixels.
`PlotSVG`	1 for vector (SVG), 0 for raster. The web version draws SVG only.
`PlotAdaptive`	1 to concentrate sample points where the curve bends (the default). Turn it off for rapidly oscillating functions, which can lose peaks.
`PlotStep`	Mesh size for colour maps.
`PlotPalette`	Colour palette 0 to 9 for colour maps.
`PlotSmooth`	1 for a smooth gradient, 0 for isobands.
`PlotShadows`	1 to shade colour maps.
`PlotLightDir`	Direction of the light, 0 to 7 clockwise from north.

The same settings are on the Calculation tab of the Settings dialog, which sets the defaults for every worksheet. The Plots & Diagrams tab of the ribbon has buttons for each form and for these lines.

The buttons under a plot

In the preview, a plot has a row of small buttons. They are not part of a printout or an export.

Plot made by	Buttons
A `plot` line or `$Plot`	Copy data, PNG, SVG
Python (matplotlib style)	Log x, Log y, 1:1, Copy data, PNG, SVG
Python (3D scene)	Copy data, PNG

Copy data puts the plotted points on the clipboard. For a plot line the data is read back from the drawing, through the axis labels, so it is correct to about four figures. PNG and SVG save the picture.

Plots in exports

Word: plots are pictures. The SVG is rasterised for Word and kept beside the picture.
Excel: a $Plot or plot becomes a native, editable XY chart with its data on a “Plot data” sheet. A colour map becomes a picture.
PDF: the printed page has the plot as drawn.

See Exporting.

Python plots

For interactive charts, subplots, 3D surfaces and plots of computed arrays, use a Python block. See Python blocks. For a chart that redraws while you drag a slider, see Interactive panels.

Related calculators: Moment and shear diagrams, Pump operating point, Concrete strength gain. More pages are in Calculators and guides.

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