You should know your data – every column, every row.
To get the min, max or mean of a quantitative vector
df <- data.frame(val1=c(-34, 45, 34, 69, 7, 99), val2=c(-14, 435, 134, 6, -7, 9))
#min of thr first col
min(df$val1)
mean(df$val1)
max(df$val1)
#or do summary on the whole data frame
summary(df)
If your data is qualitative, you can use table
animals <- c("monkeys", "monkeys", "giraffe", "donkey", "blue whale", "giraffe", "giraffe")
table(animals)
# blue whale donkey giraffe monkeys
# 1 1 3 2