Collapsing time series data by geography

[Sneha Verma]

I have some data about social movements and it includes when social movements occurred. I'm trying to aggregate the data into a bar chart that shows time differences between violent and nonviolent social movements. I have tried using:
collapse(sum) violent nonviolent by(CountryCode)
but get error messages that I cannot use time-series operators on string variables. Does anyone have advice on this? Thanks in advance!

[Nick Cox]

The error message is a guess at the problem, but wrong in your case. The syntax correction needed is a comma before the option.

collapse(sum) violent nonviolent,  by(CountryCode)

That said, you shouldn't need to collapse to get a bar chart. graph bar or graph hbar will do the calculations for you on the fly.