为R函数新增stats参数，实现按需展示指定统计量

现有一个可正常运行的R函数，需为其新增一个stats参数，实现按需展示指定统计量（如min、max、mean、median等）。例如仅需展示*均值（mean）和中位数（median）*时，可通过以下调用方式实现：

t1(data = listd, var = "sale", name = "listd", stats = c(mean, median))

示例数据集代码如下：

df <- data.frame(Name = c("asdf","kjhgf","cvbnm","rtyui","cvbnm","jhfd","cvbnm","sdfghj","cvbnm","dfghj","cvbnm"),
                 sale=c(27,28,27,16,14,25,14,14,19,18,28),
                 city=c("CA","TX","MN","NY","TX","MT","HU","KL","TX","SA","TX"),
                 Dept = c("HH","MM","NN","MM","AA","VV","MM","HU","JJ","MM","ZZ"))

内容的提问来源于stack exchange，提问作者samrr_tr