topic description

data source, the diamonds, preview of the ggplot2 package is as follows

mean(diamonds[which(diamonds$cut=="Ideal"),]$price)

problem description

1, is there a more convenient way to calculate the mean value of the y-axis of a bar chart in ggplot2?
2, is there a better way to replace it in off-table calculation?

Thank you for asking questions for the first time.