MaplePrimes - answers and comments on Question, extracting of a list (A) elements using indexes saved in another list (B)

A[B]

acer — Sun, 21 Aug 2011 05:14:24 Z

> A:=[1,3,5,2,7]:
> B:=[2,5]:

> A[B];
                             [3, 7]

Do you want list A flattened before extraction, or not?

> A:=[[1,23],[8,3],5,2,7]:
> B:=[2,5]:

> A[B];
                          [[8, 3], 7]

> ListTools:-Flatten(A)[B];
                            [23, 5]

acer

map and abs

protrader — Sun, 21 Aug 2011 06:28:11 Z

Thanks Acer,

How can I apply map function twice, one for abs and one for Mean:

with(Statistics):

DD:=[[0,4,-3,-1],[-1,-2,4,1],[1,-1,2,0]]:

I need to get this with one single like of commands:

[2,2,1]

after applying abs on every element, we calculate the Arithmetic Mean of each list in DD

functional style

Joe Riel — Sun, 21 Aug 2011 09:02:45 Z

While not the most efficient, you can do

 map((`+`@op@abs~)/nops,DD);
                                   [2, 2, 1]