Re: st: How to sum two whole rows by date and time

[Nick Cox <njcoxstata@gmail.com>]

This does sound like

. collapse ... , by(date time)

and -date time- must not appear as part of what is here represented  
by ... -as you report.

Nick


On 3 Aug 2011, at 17:39, Beatrice Crozza <beatrice.crozza@gmail.com>  
wrote:
> maybe it is an easy problem to solve, but I cannot find a way to  
> sort it out!
>
> I would like to sum the entries of two rows:
>
> date              time       x        y    d1    d2 d3  dup
> 23/01/2008     9:05     99.8           1      .   .      1
> 23/01/2008     9:05         .       5    .      1   1     2
>
> i would like to sum by date and time, in order to have:
>
> date              time       x        y    d1    d2 d3  dup
> 23/01/2008     9:05       99.8      5    1     1   1     3
>
>
> It is not always the case that, for example, one row has the price, in
> other words there is not regularity, otherwise I could have used a
> time operator to replace the row with the previous one.
>
> I also tried with collapse (sum) but i receive the error message that
> a variable cannot be both target and by() and I haven't found a
> command similar to egen rowtotal for summing columns.
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