\(\pi\) notation

This function re-expresses a vector of numbers in terms of \(\pi\), returning an expression object that can be added to a plot.

pi_notation(x, as_fraction = TRUE, as_bar = TRUE, ...)

Arguments

x	A numeric vector.
as_fraction	A logical value that defines whether or not to express sequential multipliers of \(\pi\) as fractions (TRUE) or decimals (FALSE).
as_bar	If as_fraction = TRUE, as_bar is a logical value that defines whether or not to style fractions with a horizontal bar (i.e., \(\frac{a}{b}\)) or a slash (i.e., \(a/b\)).
...	Additional arguments passed to add_lagging_point_zero if as_fraction = FALSE.

Value

The function returns an expression object.

Details

The function is designed to be used on a regular sequence of numbers (e.g., representing the tick marks on a plot) within pretty_plot.

See also

pretty_axis (and subsidiary plotting functions, such as pretty_plot) can implement this function internally.

Author

Edward Lavender

Examples

#### Example (1): Implement the function in isolation
x <- seq(0, 8, by = 0.25*pi)/pi
pi_notation(x)
#> expression("0" * pi, frac("1", "4") * pi, frac("1", "2") * pi, 
#>     frac("3", "4") * pi, "1" * pi, frac("5", "4") * pi, frac("3", 
#>         "2") * pi, frac("7", "4") * pi, "2" * pi, frac("9", "4") * 
#>         pi, frac("5", "2") * pi)
pi_notation(x, as_bar = FALSE)
#> expression("0" * pi, "1" * "/" * "4" * pi, "1" * "/" * "2" * 
#>     pi, "3" * "/" * "4" * pi, "1" * pi, "5" * "/" * "4" * pi, 
#>     "3" * "/" * "2" * pi, "7" * "/" * "4" * pi, "2" * pi, "9" * 
#>         "/" * "4" * pi, "5" * "/" * "2" * pi)
pi_notation(x, as_fraction = FALSE)
#> expression(0 * pi, 0.25 * pi, 0.5 * pi, 0.75 * pi, 1 * pi, 1.25 * 
#>     pi, 1.5 * pi, 1.75 * pi, 2 * pi, 2.25 * pi, 2.5 * pi)

#### Example (2): Plotting with fractions
## Stacked fraction
xlabels <- pi_notation(x, as_fraction = TRUE)
plot(x, rep(0, length(x)), axes = FALSE)
axis(side = 1, at = x*pi, labels = xlabels, col = "red")
## Spread fraction
x_axis <- pi_notation(x, as_fraction = TRUE, as_bar = FALSE)
plot(x, rep(0, length(x)), axes = FALSE)
axis(side = 1, at = x*pi, labels = xlabels, col = "red")

#### Example (3): Plotting with decimals
x_axis <- pi_notation(1:3, as_fraction = FALSE)
plot(x, rep(0, length(x)), axes = FALSE)
axis(side = 1, at = x*pi, labels = xlabels, col = "red")

#### Example (4): pi_notation() is implemented automatically in prettyGraphics
# ... via pretty_axis(), pretty_plot() etc.

## Define example time series of lunar phase in radians
dat <- data.frame(date = seq.Date(as.Date("2016-01-01"), as.Date("2016-02-01"), by = 1))
dat$lunar <- lunar::lunar.phase(dat$date)

## Visualise lunar phase time series, with pi_notation
pretty_plot(dat$date, dat$lunar,
            pretty_axis_args = list(pi_notation = list(NULL, list()))
            )
#> Argument 'side' not supplied to pretty_axis_args (nor 'axis_ls'); defaulting to side = 1:2.
add_moons(side = 2, pos = min(dat$date), radius = 0.5)

## Customise pi_notation
# Use as_bar = FALSE
pretty_plot(dat$date, dat$lunar,
            pretty_axis_args = list(pi_notation = list(NULL, list(as_bar = FALSE)))
            )
#> Argument 'side' not supplied to pretty_axis_args (nor 'axis_ls'); defaulting to side = 1:2.
add_moons(side = 2, pos = min(dat$date), radius = 0.5)
# Use decimals
pretty_plot(dat$date, dat$lunar,
            pretty_axis_args = list(pi_notation = list(NULL, list(as_fraction = FALSE)))
            )
#> Argument 'side' not supplied to pretty_axis_args (nor 'axis_ls'); defaulting to side = 1:2.
add_moons(side = 2, pos = min(dat$date), radius = 0.5)

## Use pi_notation within specified axis limits
pretty_plot(dat$date, dat$lunar,
            ylim = c(0, 2*pi),
            pretty_axis_args = list(pi_notation = list(NULL, list()))
            )
#> Argument 'side' not supplied to pretty_axis_args (nor 'axis_ls'); defaulting to side = 1:2.
add_moons(side = 2, pos = min(dat$date), radius = 0.5)