[R] How to extract data?

[ebashi]

I appreciate if anyone can help me,
I have a table as follow,
> rate
          DATE VALUE
1   1997-01-10  5.30
2   1997-01-17  5.30
3   1997-01-24  5.28
4   1997-01-31  5.30
5   1997-02-07  5.29
6   1997-02-14  5.26
7   1997-02-21  5.24
8   1997-02-28  5.26
9   1997-03-07  5.30
10  1997-03-14  5.30
.    ......     ...
.    ......     ...
.    ......     ...
I want to extract the DATE(s) on which the VALUE has
already dropped twice and the DATE(s) that VALUE has
already increased for three times,( ignore where
VALUE(i+1)-VALUE(i)=0),I try to use diff() function,
however that works only for one increase or decrease.

Sincerely,

Sean