R語言學習筆記（十七）：data.table包中melt與dcast函數的使用
阿新 • • 發佈：2018-01-17
eas table variable mil pat efault ast 函數 pre
melt函數可以將寬數據轉化為長數據
dcast函數可以將長數據轉化為寬數據
> DT = fread("melt_default.csv") > DT family_id age_mother dob_child1 dob_child2 dob_child3 1: 1 30 1998-11-26 2000-01-29 NA 2: 2 27 1996-06-22 NA NA 3: 3 26 2002-07-11 2004-04-05 2007-09-02 4: 4 32 2004-10-10 2009-08-27 2012-07-21 5: 5 29 2000-12-05 2005-02-28 NA > DT.m1 <- melt(DT, measure.vars = c("dob_child1", "dob_child2", "dob_child3"), + variable.name = "child", value.name = "dob") > DT.m1 family_id age_mother child dob 1: 1 30 dob_child1 1998-11-26 2: 2 27 dob_child1 1996-06-22 3: 3 26 dob_child1 2002-07-11 4: 4 32 dob_child1 2004-10-10 5: 5 29 dob_child1 2000-12-05 6: 1 30 dob_child2 2000-01-29 7: 2 27 dob_child2 NA 8: 3 26 dob_child2 2004-04-05 9: 4 32 dob_child2 2009-08-27 10: 5 29 dob_child2 2005-02-28 11: 1 30 dob_child3 NA 12: 2 27 dob_child3 NA 13: 3 26 dob_child3 2007-09-02 14: 4 32 dob_child3 2012-07-21 15: 5 29 dob_child3 NA > dcast(DT.m1, family_id + age_mother ~ child, value.var = "dob") family_id age_mother dob_child1 dob_child2 dob_child3 1: 1 30 1998-11-26 2000-01-29 NA 2: 2 27 1996-06-22 NA NA 3: 3 26 2002-07-11 2004-04-05 2007-09-02 4: 4 32 2004-10-10 2009-08-27 2012-07-21 5: 5 29 2000-12-05 2005-02-28 NA
對於較為復雜的數據可以這樣做
> DT <- fread("melt_enhanced.csv") > DT family_id age_mother dob_child1 dob_child2 dob_child3 gender_child1 gender_child2 gender_child3 1: 1 30 1998-11-26 2000-01-29 NA 1 2 NA 2: 2 27 1996-06-22 NA NA 2 NA NA 3: 3 26 2002-07-11 2004-04-05 2007-09-02 2 2 1 4: 4 32 2004-10-10 2009-08-27 2012-07-21 1 1 1 5: 5 29 2000-12-05 2005-02-28 NA 2 1 NA > DT.m2 <- melt(DT, measure = patterns("^dob","^gender"), value.name = c("dob", "gender")) > DT.m2 family_id age_mother variable dob gender 1: 1 30 1 1998-11-26 1 2: 2 27 1 1996-06-22 2 3: 3 26 1 2002-07-11 2 4: 4 32 1 2004-10-10 1 5: 5 29 1 2000-12-05 2 6: 1 30 2 2000-01-29 2 7: 2 27 2 NA NA 8: 3 26 2 2004-04-05 2 9: 4 32 2 2009-08-27 1 10: 5 29 2 2005-02-28 1 11: 1 30 3 NA NA 12: 2 27 3 NA NA 13: 3 26 3 2007-09-02 1 14: 4 32 3 2012-07-21 1 15: 5 29 3 NA NA > DT.c2 <- dcast(DT.m2, family_id + age_mother ~ variable, value.var = c("dob","gender")) > DT.c2 family_id age_mother dob_1 dob_2 dob_3 gender_1 gender_2 gender_3 1: 1 30 1998-11-26 2000-01-29 NA 1 2 NA 2: 2 27 1996-06-22 NA NA 2 NA NA 3: 3 26 2002-07-11 2004-04-05 2007-09-02 2 2 1 4: 4 32 2004-10-10 2009-08-27 2012-07-21 1 1 1 5: 5 29 2000-12-05 2005-02-28 NA 2 1 NA
R語言學習筆記（十七）：data.table包中melt與dcast函數的使用