errbar
adds vertical error bars to an existing plot or makes a new
plot with error bars. It can also make a horizontal error bar plot
that shows error bars for group differences as well as bars for
groups. For the latter type of plot, the lower x-axis scale
corresponds to group estimates and the upper scale corresponds to
differences. The spacings of the two scales are identical but the
scale for differences has its origin shifted so that zero may be
included. If at least one of the confidence intervals includes zero,
a vertical dotted reference line at zero is drawn.
errbar(x, y, yplus, yminus, cap, xlab, ylab, add=FALSE, lty=1, ylim, lwd=1, Type=rep(1,length(y)), ... )
x
representing the
group labels)
add=FALSE
. Defaults to blank for horizontal charts.
ylim
is really the
x
-axis range, excluding
differences.
1
if corresponding values represent simple estimates,
2
if they
represent differences.
Charles Geyer, University of Chicago. Modified by Frank Harrell,
Vanderbilt University, to handle missing data, to add the parameters
add
and
lty
, and to implement horizontal charts with differences.
set.seed(1) x <- 1:10 y <- x + rnorm(10) delta <- runif(10) errbar( x, y, y + delta, y - delta ) # Show bootstrap nonparametric CLs for 3 group means and for # pairwise differences on same graph group <- sample(c('a','b','d'), 200, TRUE) y <- runif(200) + .25*(group=='b') + .5*(group=='d') cla <- smean.cl.boot(y[group=='a'],B=100,reps=TRUE) # usually B=1000 a <- attr(cla,'reps') clb <- smean.cl.boot(y[group=='b'],B=100,reps=TRUE) b <- attr(clb,'reps') cld <- smean.cl.boot(y[group=='d'],B=100,reps=TRUE) d <- attr(cld,'reps') a.b <- quantile(a-b,c(.025,.975)) a.d <- quantile(a-d,c(.025,.975)) b.d <- quantile(b-d,c(.025,.975)) errbar(c('a','b','d','a - b','a - d','b - d'), c(cla[1],clb[1],cld[1],cla[1]-clb[1],cla[1]-cld[1],clb[1]-cld[1]), c(cla[3],clb[3],cld[3],a.b[2],a.d[2],b.d[2]), c(cla[2],clb[2],cld[2],a.b[1],a.d[1],b.d[1]), Type=c(1,1,1,2,2,2)) rm(x,y,delta,group,a,b,d,a.b,a.d,b.d,cla,clb,cld)