@eleonore: i see the same exception, so i don’t think ur doing anything wrong

it seems the $map function is trying to do a (get _ :speed) on a clojure.core.matrix.impl.wrappers.SliceWrapper and is returning nil

even "($map identity :speed cars)” returns a vector of nil's

i’m still using incanter 1.5.6 - ran into lots of problems (like this one) w/ 1.9.0