How to show sample error bars in the legend in R?

Question

I'm plotting data with colored error bars in R. I'd like to show "sample error bars" (with the colour used in the plot) in the legend, but how?

library("Hmisc")

d1=data.frame(x=c(1,2,3,4,5), meanY=c(1,2,3,4,5), sdY=c(1,1,1,1,1))
d2=data.frame(x=c(1,2,3,4,5), meanY=c(2.1,3.3,4.1,5.2,6.1), sdY=c(1.3,1.2,1.4,1.1,1.2))

plot(1, 1, type="n", xlab="X values", ylab="Y values", xlim=c(1,5), ylim=c(0,7))
with ( data = d1, expr = Hmisc::errbar(x, meanY, meanY+sdY, meanY-sdY, pch=1, cex=.5, cap=.0025, add=T, errbar.col="red") )
with ( data = d2, expr = Hmisc::errbar(x, meanY, meanY+sdY, meanY-sdY, pch=1, cex=.5, cap=.0025, add=T, errbar.col="green") )

legend(x="bottomright", legend=c("d1", "d2"), pch=1, pt.cex=.5)

Answer 1

Somewhat manual build of legend...

# bind data together to simplify plot code
df <- rbind(d1, d2)

# plot
with(df,
     errbar(x = x + c(rep(0.05, nrow(d1)), rep(-0.05, nrow(d2)), # dodge points to avoid overplotting
            y = meanY,
            yplus = meanY + sdY,
            yminus = meanY - sdY,
            pch = 1, cex = 0.5, cap = .0025,
            errbar.col = rep(c("red", "green"), times = c(nrow(d1), nrow(d2))),
            xlab = "X values", ylab = "Y values",
            xlim = c(1, 5), ylim = c(0, 7)))


# create data for legend
df_legend <- data.frame(x <- c(4.5, 4.5),
                        y <- c(1, 2),
                        sdy <- c(0.3, 0.3))

# add symbols to legend
with(df_legend,
  errbar(x = x,
         y = y,
         yplus = y + sdy,
         yminus = y - sdy,
         pch = 1, cex =.5, cap = .0025,
         errbar.col = c("red", "green"),
         add = TRUE))

# add text to legend
with(df_legend,
     text(x = x + 0.2,
          y = y,
          labels = c("d2", "d1")))

# add box
with(df_legend,
     rect(xleft = x - 0.2,
          ybottom = y[1] - 0.5,
          xright = x + 0.4,
          ytop = y[2] + 0.5))