R，控制double转string后的小数

Question

我有一个区域的高程矩阵。我想生成一个带有海拔的

data.frame

，colname = longitude，rowname = latitude.

原纬度为

> lat
 [1] 36.0 36.2 36.4 36.6 36.8 37.0 37.2 37.4 37.6
[10] 37.8 38.0 38.2 38.4 38.6 38.8 39.0 39.2 39.4
[19] 39.6 39.8 40.0 40.2 40.4 40.6 40.8 41.0 41.2
[28] 41.4 41.6 41.8 42.0 42.2 42.4 42.6 42.8 43.0
[37] 43.2 43.4 43.6 43.8

但是在

rownames(x) <- lat

之后，就变成了，

> rownames(x)

 [1] "36"               "36.2000007629395"
 [3] "36.4000015258789" "36.5999984741211"
 [5] "36.7999992370605" "37"              
 [7] "37.2000007629395" "37.4000015258789"
 [9] "37.5999984741211" "37.7999992370605"
[11] "38"               "38.2000007629395"
[13] "38.4000015258789" "38.5999984741211"
[15] "38.7999992370605" "39"              
[17] "39.2000007629395" "39.4000015258789"
[19] "39.5999984741211" "39.7999992370605"
[21] "40"               "40.2000007629395"
[23] "40.4000015258789" "40.5999984741211"
[25] "40.7999992370605" "41"              
[27] "41.2000007629395" "41.4000015258789"
[29] "41.5999984741211" "41.7999992370605"
[31] "42"               "42.2000007629395"
[33] "42.4000015258789" "42.5999984741211"
[35] "42.7999992370605" "43"              
[37] "43.2000007629395" "43.4000015258789"
[39] "43.5999984741211" "43.7999992370605"

里面的小数点太多了，现在变成字符了，不能用

round()

来减少小数点了

谢谢。