> # create vectors age, group, and rt > age <- c(30, 21, 20, 35, 31, 49, 34, 32) > group <- c('A', 'B', "B", "A", "A", "A", "B", 'B') > rt <- c(1.34, 1.10, 0.82, 0.96, 0.76, 1.21, 1.60, 0.67) > # create data frame stats and display it > stats <- data.frame(age, group, rt) > stats age group rt 1 30 A 1.34 2 21 B 1.10 3 20 B 0.82 4 35 A 0.96 5 31 A 0.76 6 49 A 1.21 7 34 B 1.60 8 32 B 0.67 > # show summary of the data frame > summary(stats) age group rt Min. :20.00 A:4 Min. :0.670 1st Qu.:27.75 B:4 1st Qu.:0.805 Median :31.50 Median :1.030 Mean :31.50 Mean :1.058 3rd Qu.:34.25 3rd Qu.:1.242 Max. :49.00 Max. :1.600 > # Using column numbers, show rows for the group B participants. > stats[stats[2]=='B',] age group rt 2 21 B 1.10 3 20 B 0.82 7 34 B 1.60 8 32 B 0.67 > # Using column names, show rows for reaction times < than 1 sec. > stats[stats$rt < 1, ] age group rt 3 20 B 0.82 4 35 A 0.96 5 31 A 0.76 8 32 B 0.67 > # Rows for those who are in group A AND >= 35 years old > stats[stats$group == "A" & stats$age >= 35, ] age group rt 4 35 A 0.96 6 49 A 1.21 > # Reaction times for those who are in group B OR >= 40 years old > stats$rt[stats$group == "B" | stats$age >= 40] [1] 1.10 0.82 1.21 1.60 0.67