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$I$ is commenly used as a notation of identity matrix. I am wondering is there any notation else for identity matrix?

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4 Answers

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From Wikipedia:

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It is denoted by $I_n$, or simply by $I$ if the size is immaterial or can be trivially determined by the context. (In some fields, such as quantum mechanics, the identity matrix is denoted by a boldface one, 1; otherwise it is identical to $I$.)

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It can also be written using the Kronecker delta notation:

$$(I_{n})_{ij}=\delta _{ij}.$$ Hope it helps.

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$I_n$

$I_m$

$I_n = diag(1,1,1,1\cdots,1)$

$(I_n)_{ij} =\delta_{ij}$

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You can use the notation $\mathbb{I}$ written using this code \mathbb{I}

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You could also use a "double one" like this: $\mathbb{1}$. To write it in LaTeX, you can import the package dsfont and then use \mathds{1}. You can also import bbold and then use \mathbb{1}, but this will change the appearance of your other \mathbb commands.

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