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# setIndicator -- computes the signed indicator vector of an admissible set

- Usage:
    `setIndicator(T,n)`
- Inputs:
  - T, a set,
  - n, an integer,
- Outputs:
  - a list, corresponding to a vector in $\mathbb Z^n$

## Description

Let $S$ be a set consisting of elements $s$, where $s$ is either equal to $i$ or $i^*$ with $0 \leq i \leq n-1$. The set $S$ is said to be admissible if for any integer $i$, not both $i$ and $i^{*}$ are contained in $S$. This method produces the signed indicator vector of $S$. In particular, the setIndicator of $S$ is $\sum c_ie_i \in \mathbb Z^n$ where $c_i = 1$ if $i \in T$, $c_i = -1$ if $i^{*} \in T$ and $0$ otherwise.

    i1 : S1 = set{1,2,4,5};

    i2 : S2 = set{1,"2*"};

    i3 : setIndicator(S1,7)

    o3 = {0, 1, 1, 0, 1, 1, 0}

    o3 : List

    i4 : setIndicator(S2,3)

    o4 = {0, 1, -1}

    o4 : List

If the set is not admissible it produces an error.

    i1 : S3 = set{1,"1*","2*",3}

    o1 = set {1, 1*, 2*, 3}

    o1 : Set

    i2 : setIndicator(S3,4)
    stdio:2:1:(3): error:  the signed subset is not admissible

## See also

- generalizedFlagVariety -- makes a generalized flag variety as a GKM variety

## Ways to use setIndicator:

- `setIndicator(Set,ZZ)`

## For the programmer

The object setIndicator is a method function.

The source of this document is in /build/macaulay2-88fgJW/macaulay2-1.25.11+ds/M2/Macaulay2/packages/GKMVarieties/Documentation_GKMVarieties.m2:2105:0.