用ggplot可视化正/负时间序列数据的优雅方式?

I have some time series data that represents cumulative sums of a number of data series over time, basically money flowing in and out of a market. Some are positive and some are negative, but the different strands of data do of course sum to the money flow for the market as a whole. I have been mulling over how to visualise this using I have some time series data that represents cu