[R] to avoid a do loop

[Arnaud Michel]

Hello
I have a large dataframe  (nrow=55000).
This below df1 an extract of the original dataframe

dput(df1)
structure(list(Cat = c(6, 6, 6, 6, 6, 6, 6, 6, 4, 4, 4, 4, 4,
4, 8, 8, 9, 9, 9, 9, 9, 9, 9, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 2, 2, 2, 2, 2, 2, 6, 7, 7,
7, 7, 7), Ech = c(8, 9, 10, 11, 12, 12, 13, 13, 11, 12, 13, 14,
14, 14, 9, 10, 5, 6, 7, 7, 7, 7, 7, 7, 8, 9, 10, 11, 11, 11,
4, 5, 6, 7, 8, 8, 8, 9, 9, 8, 9, 2, 3, 4, 5, 5, 5, 5, 5, 5, 5,
5, 1, 2, 3, 4, 5, 6, 6, 6, 7, 7, 7, 5, 6, 7, 8, 9, 9, 10, 10,
11, 11, 11, 11, 11, 11, 15, 5, 6, 7, 7, 8, 8, 8, 8, 9, 9, 13,
13, 14, 15, 15, 15, 10, 1, 2, 3, 4, 5)), .Names = c("Cat", "Ech"
), row.names = c("1", "2", "3", "4", "5", "6", "7", "8", "10",
"11", "12", "13", "14", "15", "17", "18", "19", "20", "21", "22",
"23", "24", "25", "27", "28", "29", "30", "31", "32", "33", "35",
"36", "37", "38", "39", "40", "41", "42", "43", "45", "46", "47",
"48", "49", "50", "51", "52", "53", "54", "55", "56", "57", "59",
"60", "61", "62", "63", "64", "65", "66", "67", "68", "69", "71",
"72", "73", "74", "75", "76", "77", "78", "79", "80", "81", "82",
"83", "84", "86", "87", "88", "89", "90", "91", "92", "93", "94",
"95", "96", "98", "99", "100", "101", "102", "103", "105", "106",
"107", "108", "109", "110"), class = "data.frame")

I do not manage to avoid a do loop because very slow
I want to obtain a new dataframe df2 with a new variable CatEch.
CatEch is the paste of the 2 variables Cat and Ech
dput(df2)
structure(list(Cat = c(6, 6, 6, 6, 6, 6, 6, 6, 4, 4, 4, 4, 4,
4, 8, 8, 9, 9, 9, 9, 9, 9, 9, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 2, 2, 2, 2, 2, 2, 6, 7, 7,
7, 7, 7), Ech = c(8, 9, 10, 11, 12, 12, 13, 13, 11, 12, 13, 14,
14, 14, 9, 10, 5, 6, 7, 7, 7, 7, 7, 7, 8, 9, 10, 11, 11, 11,
4, 5, 6, 7, 8, 8, 8, 9, 9, 8, 9, 2, 3, 4, 5, 5, 5, 5, 5, 5, 5,
5, 1, 2, 3, 4, 5, 6, 6, 6, 7, 7, 7, 5, 6, 7, 8, 9, 9, 10, 10,
11, 11, 11, 11, 11, 11, 15, 5, 6, 7, 7, 8, 8, 8, 8, 9, 9, 13,
13, 14, 15, 15, 15, 10, 1, 2, 3, 4, 5), CatEch = c("6.08", "6.09",
"6.10", "6.11", "6.12", "6.12", "6.13", "6.13", "4.11", "4.12",
"4.13", "4.14", "4.14", "4.14", "8.09", "8.10", "9.05", "9.06",
"9.07", "9.07", "9.07", "9.07", "9.07", "6.07", "6.08", "6.09",
"6.10", "6.11", "6.11", "6.11", "7.04", "7.05", "7.06", "7.07",
"7.08", "7.08", "7.08", "7.09", "7.09", "7.08", "7.09", "8.02",
"8.03", "8.04", "8.05", "8.05", "8.05", "8.05", "8.05", "8.05",
"8.05", "8.05", "8.01", "8.02", "8.03", "8.04", "8.05", "8.06",
"8.06", "8.06", "8.07", "8.07", "8.07", "6.05", "6.06", "6.07",
"6.08", "6.09", "6.09", "6.10", "6.10", "6.11", "6.11", "6.11",
"6.11", "6.11", "6.11", "7.15", "8.05", "8.06", "8.07", "8.07",
"8.08", "8.08", "8.08", "8.08", "8.09", "8.09", "2.13", "2.13",
"2.14", "2.15", "2.15", "2.15", "6.10", "7.01", "7.02", "7.03",
"7.04", "7.05")), .Names = c("Cat", "Ech", "CatEch"), row.names = c("1",
"2", "3", "4", "5", "6", "7", "8", "10", "11", "12", "13", "14",
"15", "17", "18", "19", "20", "21", "22", "23", "24", "25", "27",
"28", "29", "30", "31", "32", "33", "35", "36", "37", "38", "39",
"40", "41", "42", "43", "45", "46", "47", "48", "49", "50", "51",
"52", "53", "54", "55", "56", "57", "59", "60", "61", "62", "63",
"64", "65", "66", "67", "68", "69", "71", "72", "73", "74", "75",
"76", "77", "78", "79", "80", "81", "82", "83", "84", "86", "87",
"88", "89", "90", "91", "92", "93", "94", "95", "96", "98", "99",
"100", "101", "102", "103", "105", "106", "107", "108", "109",
"110"), class = "data.frame")
Any idea ?

-- 
Michel ARNAUD
Chargé de mission auprès du DRH
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