如何组织数据。由多个列的表吗?

I'm using the data.table package to speed up some summary statistic collection on a data set.

我使用数据。表包加速数据集中的汇总统计信息收集。

I'm curious if there's a way to group by more than one column. My data looks like this:

我很好奇，是否有一种方法可以将一个以上的列分组。我的数据是这样的:

  purchaseAmt        adShown        url   15.54            00001         150000001    4.82            00002         150000001  157.99            05005         776300044   ...               ...            ...

I can do something like this:

我可以这样做:

adShownMedian <- df1[,median(purchaseAmt),by="adShown"]

to get each ad's median. How would I do something that combines adShown and url?

得到每个广告的中位数。如何将adshow和url结合起来?

I've tried this:

我已经试过这个:

adShownMedian <- df1[,median(purchaseAmt),by=c("adShown","url")]

but no luck.

但没有运气。

Any suggestions?

有什么建议吗?

1 个解决方案

#1

Use by=list(adShown,url) instead of by=c("adShown","url")

使用by=list(adshow,url)代替by=c(“adshow”，“url”)

Example:

例子:

set.seed(007) DF <- data.frame(X=1:20, Y=sample(c(0,1), 20, TRUE), Z=sample(0:5, 20, TRUE))library(data.table)DT <- data.table(DF)DT[, Mean:=mean(X), by=list(Y, Z)]     X Y Z      Mean 1:  1 1 3  1.000000 2:  2 0 1  9.333333 3:  3 0 5  7.400000 4:  4 0 5  7.400000 5:  5 0 5  7.400000 6:  6 1 0  6.000000 7:  7 0 3  7.000000 8:  8 1 2 12.500000 9:  9 0 5  7.40000010: 10 0 2 15.00000011: 11 0 4 14.50000012: 12 0 1  9.33333313: 13 1 1 13.00000014: 14 0 1  9.33333315: 15 0 2 15.00000016: 16 0 5  7.40000017: 17 1 2 12.50000018: 18 0 4 14.50000019: 19 1 5 19.00000020: 20 0 2 15.000000