R_assignment#ch13

1.某動物園，觀察30天有關老虎、獅子和豹的出現次數，列出三種動物30天內出現次數之最大值、最小值及平均值

ch13_1 <- function()

{

 an_info <- matrix(round(rnorm(90,10,3)), ncol = 3)

 colnames(an_info) <- c("Tiger", "Lion", "Leopard")

 rownames(an_info) <- c(paste(rep("Day", times = 30), 1:30))

 print(an_info)

 apply(an_info, 2, function(x) c(max(x), min(x), round(mean(x))))

}

2.承上題，請設計含有NA之數據，再次計算最大、最小及平均值

ch13_2 <- function()

{

 an_info <- matrix(c(round(rnorm(87,10,3)),NA,NA,NA), ncol = 3, byrow = TRUE)

 colnames(an_info) <- c("Tiger", "Lion", "Leopard")

 rownames(an_info) <- c(paste(rep("Day", times = 30), 1:30))

 print(an_info)

 apply(an_info, 2, function(x) c(max(x,na.rm = TRUE), min(x,na.rm = TRUE),

                                 round(mean(x,na.rm = TRUE))))

}

3.請使用tapply函數，執行計算美國四大區之人口、面積及收入平均

ch13_3 <- function()

{

 sstr <- as.character(state.region)

 vec.pop <- state.x77[,1]

 vec.area <- state.x77[,8]

 vec.income <- state.x77[,2]

 x <- c(vec.area, vec.pop, vec.income)

 names(x) <- NULL

 Info <- matrix(c(vec.pop, vec.area, vec.income), ncol =  3)

 a.answer <- matrix(c(tapply(vec.pop, factor(sstr, levels = c("Northeast", "South",

                                                  "North Central", "West")), sum),

                      tapply(vec.area, factor(sstr, levels = c("Northeast", "South",

                                                   "North Central", "West")), sum),

                      tapply(vec.income, factor(sstr, levels = c("Northeast", "South",

                                                   "North Central", "West")), mean)),

                    nrow = 3, byrow = TRUE)

 colnames(a.answer) <- c("Northeast", "South", "North Central", "West")

 rownames(a.answer) <- c("pop", "area", "meanIncome")

 print(a.answer)

}