segment
Syntax
segment(X, [segmentOffset=true])
Arguments
X is a vector.
segmentOffset segmentOffset is a Boolean value. The default value is true.
Details
divide a vector into groups. Each group is composed of identical values next to each other. For example, [1,1,2,2,1,1,1] is divided into 3 groups: [1,1], [2,2] and [1,1,1].
Return a vector of the same length as X.
If segmentOffset=true, each element of the result is the index(in X) of the first element in each group.
If segmentOffset=false, each element of the result is its group number. Group numbers start from 0.
Examples
Ex 1.
$ x = 1 1 2 4 4 5 2 5 NULL NULL
$ segment(x);
[0,0,2,3,3,5,6,7,8,8]
$ segment(x, false);
[0,0,1,2,2,3,4,5,6,6]
Ex 2.
$ x = 1 2 1 2 1 2 1 2 1 2 1 2;
$ y = 0 0 1 1 1 2 2 1 1 3 3 2;
$ t = table(x,y);
$ select *, cumsum(x) from t context by segment(y);
y |
x |
cumsum_x |
|---|---|---|
0 |
1 |
1 |
0 |
2 |
3 |
1 |
1 |
1 |
1 |
2 |
3 |
1 |
1 |
4 |
2 |
2 |
2 |
2 |
1 |
3 |
1 |
2 |
2 |
1 |
1 |
3 |
3 |
2 |
2 |
3 |
1 |
3 |
2 |
2 |
2 |