isort

Syntax

isort(X, [ascending=true])

Arguments

X is a vector or a tuple of vectors of the same length.

ascending is a Boolean scalar or vector indicating whether to sort X (or vectors of X sequentially) in ascending order or descending order. The default value is true (ascending order).

Details

Instead of returning a sorted vector like sort!, isort returns the indexes in the original vector for each element in the sorted vector.

X[isort X] is equivalent to sort!(X).

Examples

$ x = 4 1 3 2;
$ y = isort(x);
$ y;
[1,3,2,0]
// for the sorted x: [1 2 3 4], the first element 1 is from position 1 of the original x, the second element 2 is from position 3 of the original x, ... etc.
$ x[y];
[1,2,3,4]
// equivalent to sort!(x)

$ z=isort(x, false);
$ z;
[0,2,3,1]
$ x[z];
[4,3,2,1]

$ x=2 2 1 1
$ y=2 1 1 2
$ isort([x,y]);
[2,3,1,0]
$ isort([x,y],[0,0]);
[0,1,3,2]

Sort a table based on one of its columns:

$ t2 = table(4 2 3 1 as x, 9 6 7 3 as y);
$ t2;

x	y
4	9
2	6
3	7
1	3

$ t2[isort(t2.x)];

x	y
1	3
2	6
3	7
4	9

$ t2[isort(t2.x, false)];

x	y
4	9
3	7
2	6
1	3

Sort a table based on multiple columns:

$ a=5 5 5 3 3 8 7 7;
$ b=`MSFT`GOOG`IBM`YHOO`X`YHOO`C`ORCL;
$ t=table(a,b);
$ t;

a	b
5	MSFT
5	GOOG
5	IBM
3	YHOO
3	X
8	YHOO
7	C
7	ORCL

$ t[isort([a,b], false true)];
// first sort descending on a, then sort ascending on b

a	b
8	YHOO
7	C
7	ORCL
5	GOOG
5	IBM
5	MSFT
3	X
3	YHOO

$ t[isort([a,b], false)];
// equivalent to t[isort([a,b], false false)];

a	b
8	YHOO
7	ORCL
7	C
5	MSFT
5	IBM
5	GOOG
3	YHOO
3	X