I have a dataset with hundreds of rows structured like this

```
User    Date        Value1  Value2
A       2012-01-01  4       3
A       2012-01-02  5       7
A       2012-01-03  6       1
A       2012-01-04  7       4
B       2012-01-01  2       4
B       2012-01-02  3       2
B       2012-01-03  4       9
B       2012-01-04  5       3

```

As the panel data has two indices (User=k, Date=t), I struggle to run a regression on R where the dependent variable (Value 1) is lagged only on the time index. the regression should be performed as follows: 

Value1(k,t+1) ~ Value2(k,t) 
or
Value1(k,t) ~ Value2(k,t-1)

Any suggestions?