How Do You Calculate the Means of a Data Set?

There's a lot of memory advantages to having typed data as sposed on type data. Some of some of closer's corps design is just betting that you never need the whole data set in memory. And that's a not true for the majority of science. You need means. So how does this work with being lazy in terms of, like, how do you calculate those values? Well, is this the direction we want to go? Or an i meani?