You want to add a confidence region to a graph.

Use geom_ribbon() and map values to ymin and ymax.

In the climate data set, Anomaly10y is a 10-year running average of the deviation (in Celsius) from the average 1950–1980 temperature, and Unc10y is the 95% confidence interval. We’ll set ymax and ymin to Anomaly10y plus or minus Unc10y (Figure 4-25):

library(gcookbook) # For the data set

# Grab a subset of the climate data
clim <- subset(climate, Source == "Berkeley",
               select=c("Year", "Anomaly10y", "Unc10y"))

clim

Year Anomaly10y Unc10y
 1800     -0.435  0.505
 1801     -0.453  0.493
 1802     -0.460  0.486
...
 2003      0.869  0.028
 2004      0.884  0.029