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I haven't used it, but Incanter is a Clojure statistics and data analysis thing... http://incanter.org/

That is because Lisp has fractions as a native datatype. You would get the same result in Common Lisp.

Not recommended. Matrix multiplication is really slow, even with Incanter. I doubt you'll get very far with data analysis without multiplying a few matrices so avoid.

I'm in the process right now. I didn't want to use Incanter since I don't like the kitchen sink reinvent R style, but there aren't any Clojure-esque matrix libraries around.

You, flatly, gain the language advantages of Clojure but have absolutely none of the Numpy/Matlab/R-like environments.

You need a space between the + and the first 3 (+ is the function you want to call).

So just to give you some background. In any Lisp, when you evaluate a list, the first element is treated as an operator, and the remaining items are treated as arguments. Moreover, there is no distinction between graphic characters or alphabetic characters for the purposes of defining variable names. So '+' is a valid name for a variable (which is bound to the addition function), and so is '+3'. So without the space, it thinks you are trying to call the function '+3' with the argument '3'.

If you click some of the code examples in the tutorials, it will paste them into the REPL. You have to hit enter to run them though.

Why Java, if JavaScript is so fast nowadays?

But I agree, no point to run it remotely.