"grades" <-
structure(list(prev = structure(c(3, 2, 3, 9, 9, 1, 1, 7, 1, 
7, 7, 4, 2, 4, 6, 1, 7, 1, 7, 7, 9, 9, 7, 2, 1, 1, 1, 7, 6, 3, 
3, 4, 1, 7, 1, 7, 7, 1, 4, 9, 4, 8, 3, 7, 7, 3, 1, 2, 2, 5, 7, 
1, 9, 1, 4, 9, 7, 9, 9, 6, 8, 8, 9, 4, 8, 7, 5, 4, 4, 1, 1, 7, 
7, 9, 7, 1, 1, 7, 4, 9, 1, 8, 7, 1, 8, 3, 1, 9, 4, 7, 3, 1, 1, 
7, 9, 5, 1, 9, 7, 9, 7, 1, 7, 9, 8, 8, 8, 4, 7, 5, 9, 4, 3, 1, 
9, 9, 4, 9, 9, 1, 1, 4), .Label = c(" A  ", " A- ", " B+ ", " B  ", 
" B- ", " C+ ", " C  ", " D  ", " F  "), class = "factor"), grade = structure(c(3, 
2, 2, 9, 9, 4, 1, 8, 1, 8, 7, 9, 1, 4, 2, 3, 9, 2, 7, 5, 6, 9, 
8, 1, 1, 1, 7, 7, 1, 4, 2, 5, 1, 8, 1, 4, 6, 4, 4, 8, 5, 9, 5, 
8, 6, 3, 8, 3, 1, 4, 8, 4, 4, 1, 7, 9, 9, 7, 8, 7, 8, 4, 5, 6, 
7, 9, 4, 4, 9, 1, 1, 8, 9, 9, 7, 7, 4, 7, 2, 1, 8, 8, 9, 1, 7, 
8, 1, 9, 3, 8, 9, 1, 1, 6, 7, 2, 1, 9, 9, 9, 9, 7, 1, 9, 7, 7, 
8, 5, 8, 7, 8, 7, 5, 2, 9, 7, 7, 9, 8, 2, 1, 4), .Label = c(" A  ", 
" A- ", " B+ ", " B  ", " B- ", " C+ ", " C  ", " D  ", " F  "
), class = "factor")), .Names = c("prev", "grade"), row.names = c("1", 
"2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", 
"14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", 
"25", "26", "27", "28", "29", "30", "31", "32", "33", "34", "35", 
"36", "37", "38", "39", "40", "41", "42", "43", "44", "45", "46", 
"47", "48", "49", "50", "51", "52", "53", "54", "55", "56", "57", 
"58", "59", "60", "61", "62", "63", "64", "65", "66", "67", "68", 
"69", "70", "71", "72", "73", "74", "75", "76", "77", "78", "79", 
"80", "81", "82", "83", "84", "85", "86", "87", "88", "89", "90", 
"91", "92", "93", "94", "95", "96", "97", "98", "99", "100", 
"101", "102", "103", "104", "105", "106", "107", "108", "109", 
"110", "111", "112", "113", "114", "115", "116", "117", "118", 
"119", "120", "121", "122"), class = "data.frame")