forestplot_example.R

#############################################
# Simple examples of how to do a forestplot #
#############################################

ask <- par(ask = TRUE)

# A basic example, create some fake data
row_names <- list(list("test = 1", expression(test >= 2)))
test_data <- data.frame(
  coef = c(1.59, 1.24),
  low = c(1.4, 0.78),
  high = c(1.8, 1.55)
)
test_data |>
  forestplot(
    labeltext = row_names,
    mean = coef,
    lower = low,
    upper = high,
    zero = 1,
    cex = 2,
    lineheight = "auto",
    xlab = "Lab axis txt"
  ) |>
  fp_add_header("Group") |>
  fp_set_style(lines = gpar(col = "darkblue"))

# demonstrate column spanning: center "Events / N" over two columns
forestplot(
  labeltext = list(list("A", "B"), list("C very long", "D")),
  mean = c(1, 2), lower = c(.5, 1), upper = c(1.5, 2.5)
) |>
  fp_add_header(fp_span("Events / N", columns = c(1, 2)))

# Print two plots side by side using the grid
# package's layout option for viewports
fp1 <- test_data |>
  forestplot(
    labeltext = row_names,
    mean = coef,
    lower = low,
    upper = high,
    zero = 1,
    cex = 2,
    lineheight = "auto",
    title = "Plot 1",
    xlab = "Lab axis txt"
  )
fp2 <- test_data |>
  forestplot(
    labeltext = row_names,
    mean = coef,
    lower = low,
    upper = high,
    zero = 1,
    cex = 2,
    lineheight = "auto",
    xlab = "Lab axis txt",
    title = "Plot 2",
    new_page = FALSE
  )

grid.newpage()
pushViewport(viewport(layout = grid.layout(1, 2)))
pushViewport(viewport(layout.pos.col = 1))
plot(fp1)
popViewport()
pushViewport(viewport(layout.pos.col = 2))
plot(fp2)
popViewport(2)

# An advanced example
library(dplyr)
library(tidyr)
test_data <- data.frame(
  id = 1:4,
  coef1 = c(1, 1.59, 1.3, 1.24),
  coef2 = c(1, 1.7, 1.4, 1.04),
  low1 = c(1, 1.3, 1.1, 0.99),
  low2 = c(1, 1.6, 1.2, 0.7),
  high1 = c(1, 1.94, 1.6, 1.55),
  high2 = c(1, 1.8, 1.55, 1.33)
)

# Convert into dplyr formatted data
out_data <- test_data |>
  pivot_longer(cols = everything() & -id) |>
  mutate(
    group = gsub("(.+)([12])$", "\\2", name),
    name = gsub("(.+)([12])$", "\\1", name)
  ) |>
  pivot_wider() |>
  group_by(id) |>
  mutate(
    col1 = lapply(id, \(x) ifelse(x < 4,
      paste("Category", id),
      expression(Category >= 4)
    )),
    col2 = lapply(1:n(), \(i) substitute(
      expression(bar(x) == val),
      list(val = mean(coef) |> round(2))
    )),
    col2 = if_else(id == 1,
      rep("ref", n()) |> as.list(),
      col2
    )
  ) |>
  group_by(group)

out_data |>
  forestplot(
    mean = coef,
    lower = low,
    upper = high,
    labeltext = c(col1, col2),
    title = "Cool study",
    zero = c(0.98, 1.02),
    grid = structure(c(2^-.5, 2^.5),
      gp = gpar(col = "steelblue", lty = 2)
    ),
    boxsize = 0.25,
    xlab = "The estimates",
    new_page = TRUE,
    legend = c("Treatment", "Placebo"),
    legend_args = fpLegend(
      pos = list("topright"),
      title = "Group",
      r = unit(.1, "snpc"),
      gp = gpar(col = "#CCCCCC", lwd = 1.5)
    )
  ) |>
  fp_set_style(
    box = c("royalblue", "gold"),
    line = c("darkblue", "orange"),
    summary = c("darkblue", "red")
  )

# An example of how the exponential works
data.frame(
  coef = c(2.45, 0.43),
  low = c(1.5, 0.25),
  high = c(4, 0.75),
  boxsize = c(0.25, 0.25),
  variables = c("Variable A", "Variable B")
) |>
  forestplot(
    labeltext = c(variables, coef),
    mean = coef,
    lower = low,
    upper = high,
    boxsize = boxsize,
    zero = 1,
    xlog = TRUE
  ) |>
  fp_set_style(lines = "red", box = "darkred") |>
  fp_add_header(
    coef = "HR" |> fp_txt_plain() |> fp_align_center(),
    variables = "Measurements"
  )

# An example using style
forestplot(
  labeltext = cbind(Author = c("Smith et al", "Smooth et al", "Al et al")),
  mean = cbind(1:3, 1.5:3.5),
  lower = cbind(0:2, 0.5:2.5),
  upper = cbind(4:6, 5.5:7.5),
  is.summary = c(FALSE, FALSE, TRUE),
  vertices = TRUE
) |>
  fp_set_style(
    default = gpar(lineend = "square", linejoin = "mitre", lwd = 3, col = "pink"),
    box = gpar(fill = "black", col = "red"), # only one parameter
    lines = list( # as many parameters as CI
      gpar(lwd = 10), gpar(lwd = 5),
      gpar(), gpar(),
      gpar(lwd = 2), gpar(lwd = 1)
    ),
    summary = list( # as many parameters as band per label
      gpar(fill = "violet", col = "gray", lwd = 10),
      gpar(fill = "orange", col = "gray", lwd = 10)
    )
  )

par(ask = ask)
# See vignette for a more detailed description
# vignette("forestplot",  package="forestplot")