[R] How to remove levels?

[Soyeon Kim]

Dear All,

My data looks like this
> new_ns
   chr nc_two nc_not_two
1    1    488         58
2    2    325        114
3    3    233         79
4    4    200        153
5    5    239         53
6    6    196        313
7    7    229         45
8    8    231        137
9    9    164        111
10  10    156         45
11  11    181         92
12  12    179         52
13  13     72         30
14  14     73         62
15  15    185         25
16  16     93         42
17  17     84         50
18  18     33         17
19  19     31         40
20  20     49          8
21  21     12         16
22  22     26         37

> new_ns$chr
 [1] 1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18 19 20 21 22
Levels: 1 10 11 12 13 14 15 16 17 18 19 2 20 21 22 3 4 5 6 7 8 9

but when I run this : plot(new_ns$chr,new_ns$nc_two)

the order of new_ns$chr is 1 10 11 12 13 14 15 16 17 18 19 2 20 21 22
3 4 5 6 7 8 9
how can fix this order to 1  2  3  4  5  6  7  8  9  10 11 12 13 14 15
16 17 18 19 20 21 22 in the plot ?
I attached the plot.

Thank you ahead.