我想使用this解决方案，两个合并两个数据。表的行名称。但它不工作。

z <- matrix(c(0,0,1,1,0,0,1,1,0,0,0,0,1,0,1,1,0,1,1,1,1,0,0,0,"RND1","WDR", "PLAC8","TYBSA","GRA","TAF"), nrow=6,
    dimnames=list(c("ILMN_1651838","ILMN_1652371","ILMN_1652464","ILMN_1652952","ILMN_1653026","ILMN_1653103"),c("A","B","C","D","symbol")))

tt <-matrix(c("GO:0002009", 8, 342, 1, 0.07, 0.679, 0, 0, 1, 0, 
        "GO:0030334", 6, 343, 1, 0.07, 0.065, 0, 0, 1, 0,
        "GO:0015674", 7, 350, 1, 0.07, 0.065, 1, 0, 0, 0), nrow=10, dimnames= list(c("GO.ID","LEVEL","Annotated","Significant","Expected","resultFisher","ILMN_1652464","ILMN_1651838","ILMN_1711311","ILMN_1653026")))

z <- as.data.frame(z)
tt <- as.data.frame(tt)

setDT(z)
setDT(tt)

merge(tt,z["symbol"],by="row.names",all.x=TRUE)

我得到错误：

Error in `[.data.table`(z, "symbol") : 
  When i is a data.table (or character vector), the columns to join by must be specified using 'on=' argument (see ?data.table), by keying x (i.e. sorted, and, marked as sorted, see ?setkey), or by sharing column names between x and i (i.e., a natural join). Keyed joins might have further speed benefits on very large data due to x being sorted in RAM.

这在data.table中是如何工作的？