Being a successful data analyst requires foundational skills like programming and statistics, as well as domain knowledge. Your decision should be based on which minor would best allow you to acquire these skills.
In line with this, if you intend to be a data analyst in an economics-related field, picking economics as a minor would give you invaluable domain knowledge.
However, if you are agnostic about which field you want to apply your data analysis to, minoring in computer science may be more valuable since the foundational skills that an economics minor teaches you, ie. statistics and modeling, you may already have. At the same time, a deeper understanding of computer science will allow you to employ more powerful tools in your data analysis which should pay dividends no matter which field you eventually go into.