# testing data
# list中每個element都是一個data frame
# 表示不同方案的差異

list(structure(list(n = c(1, 2, 3, 4, 5, 6), count = c(16L, 77L, 
159L, 152L, 73L, 23L), avg = c(9.1725, 10.2198051948052, 9.12234800838574, 
9.40023026315789, 9.84950684931507, 10.161231884058)), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -6L), .Names = c("n", 
"count", "avg")), structure(list(n = c(1, 2, 3, 4, 5, 6), count = c(16L, 
93L, 141L, 160L, 78L, 12L), avg = c(8.848125, 9.06784946236559, 
8.89146572104019, 9.39596875, 9.04123076923077, 7.22930555555556
)), class = c("tbl_df", "tbl", "data.frame"), row.names = c(NA, 
-6L), .Names = c("n", "count", "avg")), structure(list(n = c(1, 
2, 3, 4, 5, 6, 7), count = c(14L, 80L, 165L, 153L, 75L, 12L, 
1L), avg = c(9.69142857142857, 10.8685625, 10.800202020202, 11.0716013071895, 
10.80032, 10.7166666666667, 11.2257142857143)), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -7L), .Names = c("n", 
"count", "avg")), structure(list(n = c(1, 2, 3, 4, 5, 6, 7), 
    count = c(12L, 85L, 171L, 136L, 72L, 22L, 2L), avg = c(6.63916666666667, 
    7.97017647058824, 8.25945419103314, 8.49849264705882, 8.55227777777778, 
    8.73143939393939, 6.78071428571429)), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -7L), .Names = c("n", 
"count", "avg")), structure(list(n = c(1, 2, 3, 4, 5, 6, 7), 
    count = c(11L, 75L, 137L, 190L, 75L, 11L, 1L), avg = c(8.84090909090909, 
    9.1746, 8.65717761557178, 9.96431578947368, 9.80224, 11.0812121212121, 
    8.44571428571428)), class = c("tbl_df", "tbl", "data.frame"
), row.names = c(NA, -7L), .Names = c("n", "count", "avg")))