是否有一种快速计算多个向量中出现的值出现在多个其他向量中的次数？这是一个例子:
library(data.table)
names<-c(rep('apple',4),rep('banana',3),rep('cantalope',2),'date')
set.seed(38291)
v1<-data.table(municipality=rep('A',6),village=rep('1',6),
last=sample(names,6,replace=TRUE),
middle=sample(names,6,replace=TRUE),id=c(1:6))
v2<-data.table(municipality=rep('A',4),village=rep('2',4),
last=sample(names,4,replace=TRUE),
middle=sample(names,4,replace=TRUE),id=c(7:10))
v1
# municipality village last middle id
# 1: A 1 banana cantalope 1
# 2: A 1 cantalope banana 2
# 3: A 1 cantalope cantalope 3
# 4: A 1 apple apple 4
# 5: A 1 banana apple 5
# 6: A 1 apple apple 6
v2
# municipality village last middle id
# 1: A 2 date cantalope 7
# 2: A 2 apple date 8 …