根據一定的條件創建新變量

我試圖根據某些條件創建一個新變量。以下是數據的一個示例。根據一定的條件創建新變量

df <- data.frame(country = rep(c("A","B"), each = 9), 
     year = c(2000,2001,2008,2009,2010,2011,2012,2013,2014,1995,1996,1997,1998,1999,2000,2001,2002,2003), 
     number = c(1,2,9,10,11,12,13,14,15,1,2,3,4,5,6,7,8,9))

我想要做的是檢查時年= 2000和數量= 1。如果這一條件得到滿足我想要的變量「當」被「dot.com」，爲2000年及以後的所有這個特定國家的年份。如果上面的條件不滿足，我想'時'變量爲「其他」。

這是我想達到的。

structure(list(country = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("A", 
"B"), class = "factor"), year = c(2000, 2001, 2008, 2009, 2010, 
2011, 2012, 2013, 2014, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 
2002, 2003), number = c(1, 2, 9, 10, 11, 12, 13, 14, 15, 1, 2, 
3, 4, 5, 6, 7, 8, 9), when = structure(c(1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("dot.com", 
"other"), class = "factor")), .Names = c("country", "year", "number", 
"when"), row.names = c(NA, -18L), class = "data.frame")

來源

2016-09-06 Viðar Ingason

我們可以嘗試data.table

library(data.table) 
setDT(df)[,when :=if(any(year==2000 & number==1)) "dot.com" else "other" , by = country] 
df 
# country year number when 
# 1:  A 2000  1 dot.com 
# 2:  A 2001  2 dot.com 
# 3:  A 2008  9 dot.com 
# 4:  A 2009  10 dot.com 
# 5:  A 2010  11 dot.com 
# 6:  A 2011  12 dot.com 
# 7:  A 2012  13 dot.com 
# 8:  A 2013  14 dot.com 
# 9:  A 2014  15 dot.com 
#10:  B 1995  1 other 
#11:  B 1996  2 other 
#12:  B 1997  3 other 
#13:  B 1998  4 other 
#14:  B 1999  5 other 
#15:  B 2000  6 other 
#16:  B 2001  7 other 
#17:  B 2002  8 other 
#18:  B 2003  9 other

來源

2016-09-06 11:06:44 akrun

根據一定的條件創建新變量

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