如何在R中遍历data.table中的列
这个问题困扰了我整个周末。我想根据另一列的组计算列中“1”的数量。我想循环浏览许多列,我在这里给出的示例只是一个简单的例子。我认为DT1和DT2应该给出相同的结果,但显然DT1不起作用。有人能告诉我这是什么原因吗?谢谢大家!如何在R中遍历data.table中的列,r,dataframe,data.table,R,Dataframe,Data.table,这个问题困扰了我整个周末。我想根据另一列的组计算列中“1”的数量。我想循环浏览许多列,我在这里给出的示例只是一个简单的例子。我认为DT1和DT2应该给出相同的结果,但显然DT1不起作用。有人能告诉我这是什么原因吗?谢谢大家! DT <- data.table(Sample.name = c("A","B","C","A","A","B"), Class1 = c(1, 0, 1, 0, 1, 0), Class2 = c(
DT <- data.table(Sample.name = c("A","B","C","A","A","B"),
Class1 = c(1, 0, 1, 0, 1, 0),
Class2 = c(1, 1, 1, 0, 1, 1))
round.test <- colnames(DT)
round.test <- round.test[c(2, 3)]
round.test <- noquote(round.test)
DT1 <- DT[, sum((round.test[1]) == 1),
by = Sample.name]
DT2 <- DT[, sum(Class1 == 1),
by = Sample.name]
DT从列名的字符向量开始,可以使用get
获得列值:
round.test <- colnames(DT)
round.test <- round.test[c(2, 3)]
DT[, sum(get(round.test[1]) == 1), .(Sample.name)]
# Sample.name V1
#1: A 2
#2: B 0
#3: C 1
DT[, lapply(round.test, function(col) sum(get(col) == 1)), .(Sample.name)]
# Sample.name V1 V2
#1: A 2 2
#2: B 0 2
#3: C 1 1
“我想在许多列中循环”——请参见?melt
,如melt(DT,id=“Sample.name”)[value==1,table(Sample.name,variable)]
或类似内容。
DT[, lapply(.SD, function(col) sum(col == 1)), by=.(Sample.name), .SDcols=round.test]
# Sample.name Class1 Class2
#1: A 2 2
#2: B 0 2
#3: C 1 1