movingTopNIndex

Syntax

movingTopNIndex(X, window, top, [ascending=true], [fixed=false], [tiesMethod=’oldest’])

Arguments

X is a numeric/temporal vector. Note: Starting from version 2.00.10, the NULL values in X do not participate in data sorting.

window is an integer no less than 2, indicating the window size.

top is an integer greater than 1 and no greater than window.

ascending is a Boolean value indicating whether the data within a window is sorted in ascending order. True means ascending order and false means descending order.

fixed is a Boolean value, indicating whether the length of each row in the output array vector is fixed to be top. The default value is false. When fixed = true, all rows are of the same length. For the first (top - 1) windows, the indices of missing elements are replaced with NULL.

tiesMethod is a string that specifies how to select elements if there are more elements with the same value than spots available in the top N after sorting X within a sliding window. It can be:

  • ‘oldest’: select elements starting from the earliest entry into the window;

  • ‘latest’: select elements starting from the latest entry into the window.

Details

Return an array vector indicating the indices of the first top elements of X after sorted within each sliding window.

First Release

2.00.4

Examples

$ S = 2 5 6 1 2 4 5 6 9 0

$ m1 = movingTopNIndex(X=S, window=4, top=2, ascending=true, fixed=true)
$ m1;
[[00i,0],[0,1],[0,1],[3,0],[3,4],[3,4],[3,4],[4,5],[5,6],[9,6]]

$ m2 = movingTopNIndex(X=S, window=4, top=2, ascending=false, fixed=true)
$ m2;
[[00i,0],[1,0],[2,1],[2,1],[2,1],[2,5],[6,5],[7,6],[8,7],[8,7]]

$ m3 = movingTopNIndex(X=S, window=4, top=2, ascending=true, fixed=false)
$ print m3;
[[0],[0,1],[0,1],[3,0],[3,4],[3,4],[3,4],[4,5],[5,6],[9,6]]

$ S[m1[0]]
[,2,2,1,1,1,1,2,4,0]

$ S[m3[0]]
[2,2,2,1,1,1,1,2,4,0]

$ X = [5, 8, 1, 9, 7, 3, 1, NULL, 0, 8, 7, 7]
$ movingTopNIndex(X=X, window=4, top=2, ascending=true, fixed=true)
$ // Before version 2.00.10, the NULL values in X are involved in data sorting.
[[00i,0],[0,1],[2,0],[2,0],[2,4],[2,5],[6,5],[7,6],[7,8],[7,8],[7,8],[8,10]]
$ // As of version 2.00.10, the NULL values in X are ignored in data sorting.
[[00i,0],[0,1],[2,0],[2,0],[2,4],[2,5],[6,5],[6,5],[8,6],[8,6],[8,10],[8,10]]

$ X = [2, 1, 4, 3, 4, 3, 4]
$ // For the sixth window, the sorted X is 1 2 3 3 4 4.
$ // As tiesMethod is not specified, the default 'oldest' is used, meaning the first occurrence of 3 (at index 3) is selected.
$ movingTopNIndex(X,6,3)
[[0],[1,0],[1,0,2],[1,0,3],[1,0,3],[1,0,3],[1,3,5]]]

$ // As tiesMethod is set to 'latest', the latest occurrence of 3 (at index 5) is selected.
$ movingTopNIndex(X,6,3,tiesMethod="latest")
[[0],[1,0],[1,0,2],[1,0,3],[1,0,3],[1,0,5],[1,3,5]]