Sorry for the late reply and for the confusing request. Here is the reprex and hopefully it helps:
library(dplyr)
DF <- data.frame(Product=c("A","A","B","B"),
Weight_V1=c(55,62,51,44),
Weight_V2=c(65,67,71,82),
Weight_V3=c(24,53,53,46),
Body_Fat=c(54,23,42,12))
#Summary for all variables without group_by(), it works fine
sapply(DF[-1], function(x) summary(x))
#Summary for all variable with Product as CLASS, But I am not quite sure how
sapply(DF[-1] %>% group_by("Product"), function(x) summary(x))
I want to have summary for all the variables classified by the Product A and B, just like what I did in SAS above. Thanks for your help!