data1<-read.table(file="D:/R workplace/programlets/data20140424.txt",header=TRUE)
index1<- which(data1[,1]==1&data1[,3]==1)
#[1] 1 8
index2<-which(data1[,1]==1&data1[,3]==2)
#[1] 2 4 9
index3<-which(data1[,1]==2&data1[,3]==1)
#  5  6 10 11 12
index4<-which(data1[,1]==2&data1[,3]==2)
# 3 7
t.test(data1[index1,2],data1[index2,2])

t.test(data1[index3,2],data1[index3,2])

刚刚看到，多谢啦！

多谢！

用by就可以了
by(data$V1, data, function(x) t.test(V2~V3, data=x))