[R] delete rows

[sonchawan tamkaew]

Hello,

I would like to know how to delete some rows?
Suppose I have a large data frame look something like this:

x1      x2       x3     ..............
a        1      0.45
b        1      0.41
c        0      0.43
a        1      0.39
d        1      0.40
e        0      0.41
r        1      0.42
a        0      0.46
.        .       ..

I would like to have another data frame which has all columns like the 
original one but if any rows have the same values in x1, then keep only the 
first row and delet the rest. Is it any way to make it look like this?

x1      x2       x3     ..............
a        1      0.45
b        1      0.41
c        0      0.43
d        1      0.40
e        0      0.41
r        1      0.42
.        .       ..



Another question is I downloaded data from Oracle database to R which looks 
like this:
   DATE,'yyyy,ww'  TRD_AMT
1    2001,01       57.99330
2    2001,01       59.52926
3    2001,03       61.31018
4    2001,04       59.07095
5    2001,05       62.29583
6    2001,06       63.96679

It's weekly data and I would like to plot it. How could I do that?

Many thanks,

Sonchawan




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