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Plot Mathematical Functions

Source: R/plotFun.R
plotFun.Rd

Flexible plotting of mathematical functions in Cartesian, polar, and parametric form.

Usage

plotFun(
  expr,
  main = NULL,
  xlab = "",
  ylab = "",
  xlim = NULL,
  ylim = NULL,
  from = 0,
  to = 1,
  n = 500,
  args = NULL,
  add = FALSE,
  col = .useTheme,
  lwd = 1,
  lty = 1,
  grid = .useTheme,
  stamp = .useTheme,
  ...
)

Arguments

expr

expression defining the function. Either a formula (y ~ f(x)), a polar formula (r ~ f(phi)), or a list of two formulas for parametric plots.

main

main title of the plot. NULL (default) derives a title from expr. "", NA, or FALSE suppress the title and compact the top margin.

xlab, ylab

labels for the axes.

xlim, ylim

numeric vectors of length 2 defining axis limits. For Cartesian functions, xlim defaults to c(from, to). For polar and parametric plots, limits are derived from the data. If only xlim is supplied for polar/parametric plots, ylim mirrors it (ensures asp=1 renders correctly).

from, to

numeric; lower and upper bound of the parameter domain. Default from=0, to=1.

n

integer; number of evaluation points. Default 500.

args

named list of additional parameters fixed for the function expression (e.g. list(a = 2) for y ~ sin(a*x)).

add

logical; if TRUE, adds to an existing plot without redrawing axes or grid. Default FALSE.

col

color of the line. .useTheme (default) resolves to getTheme()$twin[1] - the primary accent color, consistent with lines.loess() and plotQQ().

lwd

line width. Default 1.

lty

line type. Default 1.

grid

controls drawing of the background grid. .useTheme (default) follows the active theme (getTheme()$grid). TRUE/FALSE/NA, or a named list, as for graphics::grid().

stamp

controls the corner stamp. .useTheme (default) resolves to getTheme()$stamp. TRUE/FALSE/ NULL, a string, or a named list for stamp().

...

further graphical parameters passed to graphics::par() via the internal framework.

Value

Invisibly returns a list with components x and y (the plotted coordinates after finite filtering).

Details

The function automatically detects the type of input:

  • Cartesian: y ~ f(x)

  • Polar: r ~ f(phi) or r ~ f(theta)

  • Parametric: list(x ~ f(t), y ~ g(t))

Additional parameters fixed for the expression can be passed via args.

See also

Other plot.distribution: plotProbDist(), shade()

Examples

# Cartesian
plotFun(y ~ x^2)


# Damped oscillation - add second curve to existing plot
plotFun(y ~ 3*exp(-x/5)*sin(4*x), from = 0, to = 10)
plotFun(y ~ 3*exp(-x/5)*sin(6*x), from = 0, to = 10, add = TRUE)


# Cardioid (polar)
plotFun(r ~ 2*(1 + cos(phi)), from = 0, to = 2*pi)


# Heart curve (parametric)
plotFun(
  list(
    x ~ 13*cos(t) - 5*cos(2*t) - 2*cos(3*t) - cos(4*t),
    y ~ 16*sin(t)^3
  ),
  from = 0, to = 2*pi, lwd = 2
)


# Parameter sweep
for (a in 1:3)
  plotFun(y ~ sin(a*x), args = list(a = a),
          from = 0, to = 2*pi,
          add = (a != 1), col = a)