Cumulative sum

[#1]

Hi,

I have a question regarding cumulative sum of the data. I want to realize the following function:

original table:

a
1
1
1

Output table:

a	obs	Cum
1	1	1
	2	1
1	3	2
1	4	3
	5	3

Anyone can help?

Thanks!

[#2]

why do I must create a straight table? I have a hundred of thousands of the data to assign these values, and then I need to do statistics on it, so I don't think it's realistic to display everything in the table...