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Indexed

Indexed

Indexed[expr,i]

represents the component of expr with index i and formats as expr_i.

Indexed[expr,{i,j,…}]

represents the component with indices i, j, … and formats as expr_i,j,….

Details

Indexed can be used to indicate components of symbolic vectors, matrices, tensors, etc.
When expr is a list, Indexed[expr,i] gives expr[[i]].
When expr is a list, Indexed[expr,{i,j,…}] gives Indexed[expr[[i]],{j,…}].

Examples

Basic Examples (3)

Represent part 1 of a symbolic vector x:

For a concrete vector, it extracts the part:

Represent part 1,2 in a symbolic matrix x:

For a concrete matrix, it extracts the part:

Use Indexed to work with symbolic vector variables:

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