在R中的lineplot.CI函数中使用子集需要帮助

I am a statistics and an R novice who is learning alot about both using RStudio. I have a imported a dataframe with the data in long form for mixed effects ANOVA on a longitudinal balanced study design. I have the following headings on my data: Treatment, Subject, Date, Age, and Volume. I have no trouble plotting either by Age group alone or Treatment group alone with the following code:I am a statistics and an R novice who is learni