Average list of list of parameter values [duplicate]

Question

I have a list of lists of fitted parameter values, e.g.

list={{a->1,b->10},{a->2,b->20},{a->3,b->30}}

(the actual parameter names can vary, as well as the size of the list)

What is the easiest way then to obtain the average parameter values, in this case avg={a->2,b->20} ?

$\begingroup$ Also: (4332) $\endgroup$
– Mr.Wizard
Commented Feb 16, 2016 at 14:10 — Mr.Wizard, Commented Feb 16, 2016 at 14:10

kglr · Accepted Answer · 2015-05-01 09:29:15Z

4

Normal@Merge[Mean][list]
(* {a -> 2, b -> 20} *)

answered May 1, 2015 at 9:29

kglr

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$\begingroup$ Perfect - thanks a lot!! $\endgroup$
– Tom Wenseleers
Commented May 1, 2015 at 9:31
1

$\begingroup$ This is nifty: is it efficient? What if the list is very very long? Does going through Association have a penalty? $\endgroup$
– chris
Commented May 1, 2015 at 9:58
$\begingroup$ @Tom, my pleasure. Thank you for the accept. $\endgroup$
– kglr
Commented May 1, 2015 at 13:20
$\begingroup$ @chris, good question. I am not sure about the relative efficiency. It would be a good idea to do timing comparisons after a few more alternatives come in. $\endgroup$
– kglr
Commented May 1, 2015 at 13:27

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C. E. · Accepted Answer · 2015-05-01 10:24:05Z

1

A method that works on older versions of Mathematica is this:

{a, b} -> Map[Mean, Transpose[{a, b} /. list]]

but admittedly it won't be as fast as Merge.

answered May 1, 2015 at 10:24

C. E.♦

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2 Answers 2