如何在显示矩阵时删除字符串值中的引号？

Reproducible example:

可重复的例子：

adfcstable <- function(d, max = 5) {
d <- as.data.frame(d)
LevelADFtable <- matrix(, nrow = dim(d)[[2]]*3, ncol = 9) #18x9
FirstDiffADFtable <- matrix(, nrow = dim(d)[[2]]*3, ncol = 8)  #18x8
Result <- matrix(, nrow = dim(d)[[2]]*3, ncol = 1)   # 18x1
ADFtable <- cbind(LevelADFtable, FirstDiffADFtable, Result) # 18 x 18
colnames(ADFtable) <- c("var","type","levelt","Pc","c","Pt","t","prob","omlo","type","1stDifft","Pc","c","Pt","t","prob","omlo","result")

for (i in as.integer(1:dim(d)[[2]])) {
 for (j in as.integer(1:3)) {
   ADFtable[3*(i-1) + j,1] <- colnames(d)[[i]]
   }
ADFtable[3*i-2,2] <- "dt"
ADFtable[3*i-2,10] <- "dt"
ADFtable[3*i-1,2] <- "d"
ADFtable[3*i-1,10] <- "d"
ADFtable[3*i,2] <- "-"
ADFtable[3*i,10] <- "-"
}
ADFtable
}

repexa <- as.data.frame(matrix(c(rnorm(10), rnorm(10), rnorm(10), rnorm(10), rnorm(10), rnorm(10)),ncol=6),stringsAsFactors = FALSE)
adfcstable(repexa)
#      var  type levelt Pc c  Pt t  prob omlo type 1stDifft Pc c  Pt t  prob
# [1,] "V1" "dt" NA     NA NA NA NA NA   NA   "dt" NA       NA NA NA NA NA  
# [2,] "V1" "d"  NA     NA NA NA NA NA   NA   "d"  NA       NA NA NA NA NA 
adfcstable <