根据源数据，为ggplot2提供各种数据。比如，平均数，标准差，标准误，置信区间。-## Summarizes data.

## Gives count, mean, standard deviation, standard error of the mean, and confidence interval (default 95 ).

##　 data: a data frame.

##　 measurevar: the name of a column that contains the variable to be summariezed

##　 groupvars: a vector containing names of columns that contain grouping variables

##　 na.rm: a boolean that indicates whether to ignore NA s

##　 conf.interval: the percent range of the confidence interval (default is 95 )