set_xaxis: Set the x-axis

Description

Set the limits, tick marks and scale of the x-axis of the CI columns, and add vertical lines to them.

Usage

set_xaxis(plot, xlim, ticks_at, ticks_digits, ticks_minor, x_trans, vline)

Value

A forest plot object.

Arguments

plot: A forest plot object, see forest.
xlim: Limits for the x-axis as a vector of length 2, i.e. c(low, high). By default the minimum and maximum of the lower and upper values are used.
ticks_at: Tick mark positions. By default, ticks are computed automatically: pretty for linear axes and a decade-aware helper for log scales (e.g. 0.1, 1, 10, 100 for a wide log10 range).
ticks_digits: Number of digits for the tick labels. If an integer is given, for example 1L, trailing zeros after the decimal mark are dropped. Give a double, for example 1, to keep them. By default the number is calculated from the tick positions. Use a list to mix the two between CI columns, as a vector makes them all double.
ticks_minor: A numeric vector of positions to draw ticks without labels. It can be a superset of ticks_at or disjoint from it.
x_trans: Scale of the axis, one of "none" (default), "log", "log2" or "log10". Use "log" if the values are exponential, e.g. odds ratios or hazard ratios. The default reference line of forest is 1 for log scales and 0 otherwise.
vline: Numeric vector, positions of vertical lines drawn in addition to the reference line, on the original scale of the x-axis. Their look is set with vertline of forest_style. No lines are drawn by default.

Details

Arguments left out keep their current value, so the axis can be set in several calls, and NULL goes back to the default. A single value applies to all CI columns. To give the columns different settings, provide a list with one element for each CI column (a vector for ticks_digits and x_trans), where NA leaves a column at its default.

This builds the plot again, so it must be used before the plot is edited with edit_plot, add_text, insert_text, add_border or add_grob.

Examples

Run this code

library(grid)
# Read provided sample example data
dt <- read.csv(system.file("extdata", "example_data.csv", package = "forestploter"))
dt <- dt[1:6, ]

# Add a blank column for the forest plot to display CI
dt$` ` <- paste(rep(" ", 20), collapse = " ")

p <- forest(dt[, c("Subgroup", " ")],
            est = dt$est,
            lower = dt$low,
            upper = dt$hi,
            ci_column = 2,
            ref_line = 1)

# Limits and tick marks, with a vertical line at 2
p <- set_xaxis(p, xlim = c(0, 4), ticks_at = c(0.5, 1, 2, 3), vline = 2)
plot(p)

# The axis can be set in several calls, `NULL` goes back to the default
p <- set_xaxis(p, ticks_digits = 1L)
p <- set_xaxis(p, vline = NULL)

# A log scale, where the reference line of `forest()` defaults to 1
plot(set_xaxis(p, x_trans = "log", xlim = c(0.25, 4), ticks_at = c(0.5, 1, 2, 4)))