hey guys… What am I doing wrong?…

https://cloojure.github.io/doc/core.matrix/clojure.core.matrix.dataset.html#var-join-columns

looks like you need datasets, not vectors?

boot.user=> (set-env! :resource-paths #{"src"} :dependencies '[ [net.mikera/core.matrix "0.56.0"]])
boot.user=> (use 'clojure.core.matrix.dataset)
boot.user=> (clojure.core.matrix.dataset/join-columns (dataset [:a :b :c] [[1 4 7]]) (dataset [:d :e :f] [[2 5 8]]) (dataset [::g :h :i] [[3 6 9]]))
#dataset/dataset {:column-names [:a :b :c :d :e :f :boot.user/g :h :i], :columns [[1] [4] [7] [2] [5] [8] [3] [6] [9]], :shape [1 9]} 

Thanks!

You're welcome, @chokheli