[R] Finding the Summation of Monthly Amount

[dila radi]

Hi all,

Could someone help me on this? I have this kind of data set

structure(list(Year = c(1971L, 1971L, 1971L, 1971L, 1971L, 1971L,
1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L,
1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L,
1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L,
1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L,
1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L,
1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L,
1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L,
1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L,
1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L, 1971L,
1971L, 1971L, 1971L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L,
1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L,
1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L,
1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L,
1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L,
1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L,
1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L,
1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L,
1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L,
1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L, 1972L,
1972L, 1972L, 1972L, 1972L, 1973L, 1973L, 1973L, 1973L, 1973L,
1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L,
1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L,
1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L,
1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L,
1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L,
1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L,
1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L,
1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L,
1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L, 1973L,
1973L, 1973L, 1973L, 1973L), Month = c(1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
3L, 3L, 3L, 3L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L,
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L), Rain = c(68, 6, 6.3, 55.3,
18.2, 1.2, 5.3, 0, 0, 1.2, 0.2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2.5,
0, 0, 12.1, 0.5, 0, 0, 0, 0, 0, 0, 0.5, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 50.8, 7.1, 0, 0, 0, 4, 22, 14.7, 0, 17.7, 0,
106.6, 0, 4.8, 14.7, 2.2, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 8.6, 3.3, 0, 16.7, 0, 5.8, 9.1, 0, 0, 0, 0, 0, 0, 0, 12.6,
12.9, 0, 0, 0, 0, 0, 3.3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 50.7,
1.2, 2.5, 0, 0, 0, 0, 17, 0, 2.5, 0, 0, 0, 0, 3.8, 0, 0, 0, 0,
0, 0, 2.7, 2.7, 12.6, 0, 0, 0, 0, 0, 0, 0, 3.3, 0, 0, 5.5, 2.5,
0, 35.5, 5, 3.3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6.3,
0, 0, 0, 5.8, 0, 0, 0, 15.4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5.5,
30.2, 64.5, 0, 11.9, 3.8, 3.3, 7.1, 27.9, 32, 106.6, 0.2, 0,
5.3, 4.5, 0, 0, 1.5, 11.9, 6.6, 0, 0, 11.9, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 8.3, 8.1, 0.5, 0, 0, 0, 0, 0, 0, 0, 0, 30.9, 1.2,
0, 0, 9.3, 82.5, 16.5, 0, 0, 0, 0.7, 0, 0, 36, 0, 3.8, 0, 0,
0, 0, 0, 0, 0, 4.3, 0, 0, 38, 8.8, 0, 26.4, 0, 0, 0.7, 13.4,
9.6, 8.3, 0, 3.8, 8.8, 0, 45.7, 1.2, 12.9, 0, 0, 0, 21.3, 1,
0)), .Names = c("Year", "Month", "Rain"), class = "data.frame", row.names =
c(NA,
-271L))

and I want to find the sum of Rain in column 3 according to their month.
How could I achieved this so that it would appear as follow:

structure(list(Year = c(1971L, 1971L, 1971L, 1972L, 1972L, 1972L,
1973L, 1973L, 1973L), Month = c(1L, 2L, 3L, 1L, 2L, 3L, 1L, 2L,
3L), Rain = c(176.8, 228.2, 90.9, 81, 73.1, 127.7, 242.8, 189.5,
204.2)), .Names = c("Year", "Month", "Rain"), class = "data.frame",
row.names = c(NA,
-9L))

Thank you so much

Dila

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