From: Peter on
Hi. Have search already for couple hours but cannot find a solution. Suppose i have the following matrix

'1-1-1999' 1
'1-2-1999' 2
'1-3-1999'
'1-1-1999' 3
'1-2-1999' 4
'1-3-1999' 6

but i need it in this format:

'1-1-1999' 1 3
'1-2-1999' 2 4
'1-3-1999' 6

indeed there is missing data, i need to have it. it is allowed to be NaN.

could anyone give a hint? Thanks alot