isort

isort(X, [ascending=true])

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).

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).

x = 4 1 3 2;
y = isort(x);
y;
// output
[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];
// output
[1,2,3,4]
// equivalent to sort!(x)

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

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

t2[isort(t2.x)];

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

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;

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

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