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Plot the Exact Power Curve around a Sample Size Solution

Source: R/plot.bbssr_samplesize.R
plot.bbssr_samplesize.Rd

Recomputes the exact power over a range of sample sizes of group 2 and marks the selected sample size and the target power.

Usage

# S3 method for class 'bbssr_samplesize'
plot(
  x,
  N2.range = NULL,
  main = NULL,
  sub = NULL,
  xlab = NULL,
  ylab = NULL,
  ylim = NULL,
  ref.line = NULL,
  ref.line.N2 = NULL,
  show.points = TRUE,
  colours = NULL,
  base_size = 11,
  ...
)

Arguments

x

An object of class bbssr_samplesize returned by BinarySampleSize

N2.range

Optional integer vector of sample sizes of group 2 at which the power is evaluated. By default the selected sample size plus or minus five is used

main

Title of the plot. The default of NULL builds the title from the object and a single NA drops it

sub

Subtitle of the plot, following the convention of main

xlab

Label of the horizontal axis, following the convention of main

ylab

Label of the vertical axis, following the convention of main

ylim

Numeric vector of length two giving the range of the vertical axis, or NULL for a range chosen from the data

ref.line

Numeric vector of heights at which a dashed horizontal line is drawn. The default of NULL places one line at the target power and a single NA draws no line

ref.line.N2

Numeric vector of positions at which a dotted vertical line is drawn. The default of NULL places one line at the selected sample size and a single NA draws no line

show.points

Logical. If TRUE, the default, a marker is drawn at every evaluated sample size. Set it to FALSE to draw the curve alone, which is easier to read over a wide range

colours

Colour of the curve

base_size

Base font size of the theme, in points

...

Further arguments, currently ignored

Value

A ggplot object

Details

The power is recomputed at every point of N2.range, so a wide range combined with one of the unconditional tests can take a long time to evaluate.

The vertical range is imposed with coord_cartesian, so points outside ylim are hidden rather than removed from the data.

Examples

# \donttest{
ss <- BinarySampleSize(p1 = 0.4, p2 = 0.2, r = 1, alpha = 0.025,
                       tar.power = 0.8, Test = 'Chisq')
plot(ss)


# Enlarge the type, rename the axes and draw neither reference line
plot(ss, base_size = 14, ref.line = NA, ref.line.N2 = NA,
     xlab = 'Sample size of the control group', ylab = 'Exact power')

# }