I'm trying to create a bubble chart with "Average item price" in Y axis, and "Average basket price" in X axis. I can create "Average item price" in Y axis without any problems. However, I only see Histogram as an option for X axis to display custom X axis, and it only lets me use the actual field values. Is it possible to use any aggregations on the X axis like sum, average, mean, etc.?
Not with any of the existing visualizations in Kibana, they all use bucketing data (aggregations) for the x-axis.
You might be able to get a close approximation of the tends you're looking for with the Histogram though. For example, if you were to bucket on the total basket price for the x-axis and use the average item price as the metric on the y-axis, you might get an idea of if it were a few number of expensive items or a large number of cheap items driving large orders. I'm not entirely sure that would work though, or if that's even the information you want.