Subchapters:

Working with arrays

One of the things IDL is able to do is working with arrays very nicely.
First, let's define some arrays:

        IDL> vec1 = [1,2,3,4,3,2,3,4,5,5,3]
        IDL> vec2 = [8,65,7,54,3,4,6,7,6,5,5]
        IDL> tab1 = [ [ 1.5 , 2 , 3 ] , [ 2 , 3 , 4 ] , [ 7 , 9 , 0 ] ]

this latest one is a 2D array.

Arrays are in the [ column , row ] order.

Arrays start at 0!!!

=> the 5th column of tab[N,M] is tab[4,*]

There is a large set of other array-oriented arithmetic functions, such as expand, mean, rebin, reverse, smooth, sort, total, transpose, and so forth.