Merging Files and Grouping by several variables

[lmd021]

I have three data files that separate brain regions by hemisphere. What code can I use to merge multiple files to combine their data and then group by age/gender:

region 1 male 10-15 years "data average"
region 1 male 16-20 years "data average"
region 1 female 10-15 years "data average"
region 1 female 16-20 years "data average"

[nirgrahamuk]

I don't see how we can give you a detailed answer without knowing the structure of the three files.
Are you able to load the files, even as unmerged ?
if so can you make a reprex from the 3 ?
Please have a look at this guide, to see how to create one:

FAQ: How to do a minimal reproducible example ( reprex ) for beginners

A minimal reproducible example consists of the following items: A minimal dataset, necessary to reproduce the issue The minimal runnable code necessary to reproduce the issue, which can be run on the given dataset, and including the necessary information on the used packages. Let's quickly go over each one of these with examples: Minimal Dataset (Sample Data) You need to provide a data frame that is small enough to be (reasonably) pasted on a post, but big enough to reproduce your issue. Let's say, as an example, that you are working with the iris data frame head(iris) #> Sepal.Length Sepal.Width Petal.Length Petal.Width Species #> 1 5.1 3.5 1.4 0.…