error_bars: Add Error Bars to a Plot

In rettopnivek/arfpam: Assorted R Functions for Processing, Analysis, and Modeling

Add Error Bars to a Plot

Description

Adds error bars to an existing plot.

Usage

error_bars(
  pos,
  limits = NULL,
  lb = NULL,
  ub = NULL,
  arrow = TRUE,
  flip = FALSE,
  length = 0.05,
  code = 3,
  angle = 90,
  border = NULL,
  ...
)

Arguments

pos	Either a single value or a numeric vector of N values indicating the position(s) at which an error bar should be drawn.
limits	Either a vector of 2 values or a 2 x N matrix giving the lower and upper limits, respectively, of the error bars.
lb	A vector of N values with the lower limits for the error bars.
ub	A vector of N values with the upper limits for the error bars.
arrow	Logical; if TRUE, arrows are drawn at each position, otherwise a call is made to polygon to create a filled-in segment to represent connected error bars.
flip	Logical; if TRUE, bars are drawn horizontally instead of vertically. In this case pos denotes the position(s) on the y-axis. Otherwise, pos denotes the position(s) on the x-axis.
length	The length of the arrowhead for the call to arrows.
code	Integer controlling whether to draw an arrowhead at the start (1), end (2), or at both ends (3) of the line for the call to arrows.
angle	The angle of the lines creating the arrowhead for the call to arrows. Using 90 degrees results in a flat bar per standard error bars.
border	The color to draw the border for polygon.
...	Additional plotting parameters for the arrows function, or if arrow is FALSE, polygon.

Examples

# Simulate 5 variables with increasing means
dtf <- lapply(lin(-.5, .5, 5), function(x) rnorm(100, mean = x))
names(dtf) <- paste0("V", 1:5)
dtf <- data.frame(dtf)
# Extract sample means and standard errors
sm <- data.frame(
  M = colMeans(dtf),
  SE = apply(dtf, 2, sem)
)
# Compute 95% confidence intervals around
# sample means
sm$LB <- sm$M + qnorm(.025) * sm$SE
sm$UB <- sm$M + qnorm(.975) * sm$SE

# Plot mean for each variable
plot(1:5, sm$M,
  pch = 19,
  xlab = "Variable", ylab = "Mean", ylim = c(-1, 1)
)
# Add error bars (as arrows) for 95% confidence intervals
error_bars(1:5, rbind(sm$LB, sm$UB))
# Add error bars (as connected filled segment)
error_bars(1:5, rbind(sm$LB, sm$UB),
 arrow = FALSE, col = rgb(.5, .5, .5, .2), border = NA
)

# Histogram for draws from standard normal
set.seed(300)
x <- rnorm(1000)
hist(x,
  col = "grey", border = "white", main = "",
  xlab = "z-scores", freq = FALSE, xlim = c(-4, 4)
)
# Add horizontal bars showing difference between
# 95% and 68% coverage interval
error_bars(c(.1, .3),
  lb = qnorm(c(.025, .16)), ub = qnorm(c(.975, .84)),
  lwd = 2, flip = TRUE
)
# Label bars
text(c(-2.1, -1.1), c(.1, .3),
  c("95%", "68%"),
  pos = 2
)

rettopnivek/arfpam documentation built on Oct. 20, 2024, 7:24 p.m.