Plot a Function

Description

Plots mathematical expressions in one variable using the formula syntax.

Usage

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PlotFun(FUN, args = NULL, from = NULL, to = NULL, by = NULL,
        xlim = NULL, ylim = NULL, polar = FALSE, type = "l",
        col = par("col"), lwd = par("lwd"), lty = par("lty"),
        pch = NA, add = FALSE, ...)

Arguments

FUN

a mathematical expression defined using the formula syntax: f(x) ~ x.

args

a list of additional parameters defined in the expression besides the independent variable.

from, to

the range over which the function will be plotted.

by

number: increment of the sequence.

xlim, ylim

NULL or a numeric vector of length 2; if non-NULL it provides the defaults for c(from, to) and, unless add = TRUE, selects the x-limits of the plot - see plot.window.

polar

logical. Should polar coordinates be used? Defaults to FALSE.

type

plot type: see plot.default

col

colors of the lines.

lwd

line widths for the lines.

lty

line type of the lines.

pch

plotting 'character', i.e., symbol to use.

add

logical; if TRUE add to an already existing plot; if NA start a new plot taking the defaults for the limits and log-scaling of the x-axis from the previous plot. Taken as FALSE (with a warning if a different value is supplied) if no graphics device is open.

...

the dots are passed to the plot, resp. lines function.

Details

A function can be plotted with curve. This function here adds some more features, one enabling to use a formula for defining the function to plot. This enables as well a parametric equation to be entered straight forward. Parameters of a function can be set separatedly. The aspect ratio y/x will be set to 1 by default. (See plot.window for details.)

If axes are not set to FALSE centered axis at a horizontal and vertical position of 0 will be drawn, containing major and minor ticks.

Author(s)

Andri Signorell <andri@signorell.net>

See Also

curve

Examples

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par(mfrow=c(3,4))

# Cartesian leaf
PlotFun(3*a*z^2 /(z^3+1) ~ 3*a*z /(z^3+1+b), args=list(a=2, b=.1), from=-10, to=10, by=0.1,
        xlim=c(-5,5), ylim=c(-5,5), col="magenta", asp=1, lwd=2 )

# family of functions
PlotFun(a*exp(-x/5)*sin(n*x) ~ x, args=list(n=4, a=3), from=0, to=10, by=0.01,
        col="green")

PlotFun(a*exp(-x/5)*sin(n*x) ~ x, args=list(n=6, a=3), from=0, to=10, by=0.01,
        col="darkgreen", add=TRUE)

# cardioid
PlotFun(a*(1+cos(t)) ~ t, args=list(a=2), polar=TRUE, from=0, to=2*pi+0.1, by=0.01, asp=1)

PlotFun(13*cos(t) - 5*cos(2*t) - 2*cos(3*t) - cos(4*t) ~ 16*sin(t)^3,
        from=0, to=2*pi, by=0.01, asp=1, xlim=c(-20,20), col="red", lwd=2)


PlotFun(a*sin(2*t)*cos(2*t) ~ t, args=list(a=6), polar=TRUE, from=0, to=2*pi+0.1, by=0.01,
        col="orange")

# astroid
PlotFun(a*sin(t)^3 ~ a*cos(t)^3, args=list(a=2), from=0, to=2*pi+0.1, lwd=3, by=0.01,
        col="red")

# lemniscate of Bernoulli
PlotFun((2*a^2*cos(2*t))^2 ~ t, args=list(a=1), polar=TRUE, from=0, to=2*pi+0.1, by=0.01,
        col="darkblue")

# Cycloid
PlotFun(a*(1-cos(t)) ~ a*(t-sin(t)), args=list(a=0.5), from=0, to=30, by=0.01,
        col="orange")

# Kreisevolvente
PlotFun(a*(sin(t) - t*cos(t)) ~ a*(cos(t) + t*sin(t)), args=list(a=0.2), from=0, to=50, by=0.01,
        col="brown")


PlotFun(sin(2*t) ~ sin(t), from=0, to=2*pi, by=0.01, col="blue", lwd=2)

# multiple values for one parameter
sapply(1:3, function(a) PlotFun(sin(a*x) ~ x,
                                args=list(a=a), from=0, to=2*pi, by=0.01,
                                add=(a!=1), col=a))

PlotFun(sin(3*x) ~ x, polar=TRUE, from=0, to=pi, by=0.001, col=hred, lwd=2)


PlotFun(1 + 1/10 * sin(10*x) ~ x, polar=TRUE, from=0, to=2*pi, by=0.001, col=hred)
PlotFun(sin(x) ~ cos(x), polar=FALSE, from=0, to=2*pi, by=0.01, add=TRUE, col="blue")

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