# indices(RingElement) -- indices of variables occurring in a polynomial

## Synopsis

• Usage:
indices f
• Function: indices
• Inputs:
• f, , or over a polynomial ring
• Outputs:
• a list, of integers, the indices of the variables occurring in the polynomial or matrix

## Description

The first variable in a polynomial ring has index 0, the second has index 1, etc. This function returns a list (in ascending order) of the indices of all of the variables that occur in f.
 ```i1 : R = QQ[a..g] o1 = R o1 : PolynomialRing``` ```i2 : F = a^3+b^2*c+3*f^10*d-1+e-e 10 3 2 o2 = 3d*f + a + b c - 1 o2 : R``` ```i3 : indices F o3 = {0, 1, 2, 3, 5} o3 : List``` ```i4 : index a o4 = 0``` ```i5 : support F o5 = {a, b, c, d, f} o5 : List```
The same works for matrices.
 ```i6 : M = matrix"a+b,c+e;2a-e,3b-c4" o6 = | a+b c+e | | 2a-e -c4+3b | 2 2 o6 : Matrix R <--- R``` ```i7 : indices M o7 = {0, 1, 2, 4} o7 : List``` ```i8 : support M o8 = {a, b, c, e} o8 : List```
This use of indices has no relationship with the use for specifying parts of a direct sum