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IdentityMatrix

IdentityMatrix[n]
gives the n

n identity matrix.

The option WorkingPrecision can be used to specify the precision of matrix elements.

IdentityMatrix[n, SparseArray] gives the identity matrix as a SparseArray object.

Construct a 3×3 identity matrix:

Out[1]//MatrixForm=

Construct a 3×4 identity matrix:

Create a machine-precision identity matrix:

Use DiagonalMatrix for general diagonal matrices:

The KroneckerProduct of a matrix with the identity matrix is a block diagonal matrix:

The WorkingPrecision option is equivalent to creating the matrix, then applying N:

IdentityMatrix gives a matrix with dense storage. SparseArray is more compact:

The SparseArray representation uses a fraction of the memory:

For matrix and arithmetic operations they are effectively equal:

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