Q1
宅男Jason某日统计了DC超级英雄电影中6个英雄巨头杀敌人数如下：
superhero_kills <- c(“superman kills 1030 enemies.”, “wonderwoman kills 206 enemies.”, “aquaman kills 32 enemies.”, “cyborg kills 17 enemies.”, “batman kills 4 enemies.”, “the flash kills 0 enemies.”)
他想考考自己的女朋友Rian知不知道这些超级英雄到底打败了多少敌人，但是懒得把里面的数字一个一个改成X。他想到在Data Maniac的课堂上学习了sub（）函数，并且了解到在R中，\s代表空格，([0-9]+)代表任何出现的数字。他希望可以得到结果如下：
[1] “superman kills X enemies.” “wonderwoman kills X enemies.” “aquaman kills X enemies.” “cyborg kills X enemies.”
[5] “batman kills X enemies.” “the flash kills X enemies.”
那么请你来帮助他完成这个甜蜜的任务吧!
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Q2:
Data Maniac 班上有很多可爱的同学，他们的信息被我们偷偷收集了，以下是班上14名同学的基本信息：
name <- c(“Jennifer”, “Thalia”, “Ken”, “Elaine”," Jason“,”Chris“,”Lily“,”Odelia“,”Martin“,”Isabel“,”Jane“,”Connie“,”Elisa“，”Cherry")
age <- c(16, 17, 14, 17 , 29 , 19 , 21, 18, 19, 23, 17, 19, 22, 21)
hair <- c(“black”, “green”, “black”, “brown”, “white”, “black”, “purple”, “black”, “blue”, “black”, “green”, “silver”, “green”, “black”)
为了更好的分析，我们用以下方法把这些数据转变为data.frame，并命名为classmates。
Create data frame
classmates <- data.frame(name, age, hair)
classmates <- data.frame(name, age, hair)
你需要协助Jason用课上学到的dplyr包完成以下任务： 1. 同学中选出所有19岁及以下的； 2. 在上一个任务的基础上选出黑色头发的； 3. 接着根据年龄从大到小将这些黑发及19岁以下的同学进行排序； 4. 计算出满足以上条件同学的平均年龄及最小年龄,分别命名为mean_age1和min_age1 提示：以上任务你需要用%>%来完成。
- 计算出所有14位同学的平均年龄，最大及最小年龄，分别命名为mean_age2和max_age及min_age2。
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