reshape2数据汇总

• dcast：长数据变短数据，数据变形，汇总

长数据

name	department	title	salary
A	depart1	title1	10000
B	depart2	title1	12000
C	depart1	title2	8000
D	depart3	title2	7000
E	depart3	title3	4000
F	depart2	title3	3000

# 假设data.frame名称为mydata, 1式
dcast(mydata, name + department ~ title, sum, value.var = "salary")
# 注意value.var之后是跟一个带双引号的变量名称
# 还可以试一下, 2式
dcast(mydata, name ~ title + department, sum, value.var = "salary")

由1式，得到短数据：

name	department	title1	title2	title3
A	depart1	10000	0	0
B	depart2	12000	0	0
C	depart1	0	8000	0
D	depart3	0	7000	0
E	depart3	0	0	4000
F	depart2	0	0	3000

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• melt：短数据变长数据

短数据：

name	department	title1	title2	title3
A	depart1	10000	0	0
B	depart2	12000	0	0

# 假设data.frame名称为mydata，式1
melt(mydata, id = c("name", "department"))
# 可以试一下，式2
melt(mydata, id = "name")

由式1，得到长数据：

name	department	variable	value
A	depart1	title1	10000
B	depart2	title1	12000
A	depart1	title2	0
B	depart2	title2	0
A	depart1	title3	0
B	depart2	title3	0