rank

Syntax

rank(X, [ascending=true], [groupNum], [ignoreNA=true], [tiesMethod=’min’], [percent=false], [precision])

Arguments

X is a vector/matrix/table.

ascending is a Boolean value indicating whether the sorting is in ascending order. The default value is true (ascending).

groupNum is a positive integer indicating the number of groups to sort X into.

ignoreNA is a Boolean value indicating whether NULL values are ignored.

tiesMethod is a string indicating how to rank the group of elements with the same value (i.e., ties):

  • ‘min’ : Gives all ties the smallest rank value of the tie values.

  • ‘max’ : Gives all ties the largest rank value of the tie values.

  • ‘average’ : Gives all ties the average of the rank values for all ties.

  • ‘first’: Gives the first found tie value the lowest rank value, and continues with the following rank value for the next tie.

percent is a Boolean value, indicating whether to display the returned rankings in percentile form. The default value is false.

precision is an integer between [1, 15]. If the absolute difference between two values is no greater than 10^(-precision), the two values are considered to be equal.

Note: If parameter precision is specified, X must be numeric, and the tiesMethod cannot be specified as ‘first’.

Details

Based on the sort order specified by ascending, this function returns the ranking (starting from 0) of each element in X.

If X is a vector, return a vector with the same length as X:

  • If groupNum is specified, divide the sorted vector X into groupNum groups and return the group number (starting from 0) for each element in X.

    • If the number of elements in X cannot be divided by groupNum, the first mod(size(X), groupNum) groups will hold one more element. For example, X has 6 elements, groupNum is specified as 4, the first and second elements of sorted vector X belong to group 0, the third and fourth elements belong to group 1, and the fifth and sixth elements belong to groups 2 and 3, respectively.

    • If the identical elements are not divided in the same group, return the smallest group number for all identical elements.

  • If ignoreNA = true, NULL values are ignored and return NULL.

If X is a matrix/table, conduct the aforementioned calculation within each column of X. The result is a matrix/table with the same shape as X.

Examples

$ rank(45 16 32 21);
[3,0,2,1]

$ rank(45 16 32 21, false);
[0,3,1,2]

$ rank(9 1 6 1 3 3);
[5,0,4,0,2,2]
// two identical elements have the same ranking.

$ rank(X=9 5 4 8 1 3 6 2 7, groupNum=3);
[2,1,1,2,0,0,1,0,2]

$ rank(X=9 5 4 8 1 3 6 2 7, ascending=false, groupNum=3);
[0,1,1,0,2,2,1,2,0]

$ rank(X=1 2 2 3, tiesMethod='min');
[0,1,1,3]

$ rank(X=1 2 2 3, tiesMethod='average');
[0,1.5,1.5,3]

$ rank(X=1 2 2 3, tiesMethod='first');
[0,1,2,3]

$ rank(1 NULL NULL 3);
[0,,,1]

$ rank(X=1 NULL NULL 3, ignoreNA=false);
[2,0,0,3]

$ t=table(1 1 1 2 2 2 2 as id, 3 5 4 6 2 7 1 as x)
$ t

id

x

1

3

1

5

1

4

2

6

2

2

2

7

2

1

 
$ select *, rank(x) from t context by id;

id

x

rank_x

1

3

0

1

5

2

1

4

1

2

6

2

2

2

1

2

7

3

2

1

0