#1/8 v = c(1,5,6,2,8,7) v[5:6] v[c(3,5,6)] matrix[,3] matrix[,3,drop = F] #1/9ab airquality[2,] new_airquality = airquality[,c(1,2,5,6)] #1/9c airquality[17, ][,1] airquality[17,1] airquality$Ozone[17] airquality[17,]$Ozone #1/9d airquality[!is.na(airquality$Ozone),] nrow(airquality[!is.na(airquality$Ozone),]) sum(!is.na(airquality$Ozone)) #1/9e jo_ozone <- airquality[!is.na(airquality$Ozone),] mean(jo_ozone$Solar.R, na.rm = TRUE) #1/10/b max_Solar.R <- max(airquality$Solar.R, na.rm = TRUE) max_Solar.R <- max(airquality$Solar.R) subset(airquality, airquality$Solar.R == max_Solar.R, select = c(Month, Day))