| Mathematics | |
The Identity Matrix
Generally accepted mathematical notation uses the capital letter 
to denote identity matrices, matrices of various sizes with ones on the main diagonal and zeros elsewhere. These matrices have the property that 
and 
whenever the dimensions are compatible. The original version of MATLAB could not use 
for this purpose because it did not distinguish between upper and lowercase letters and 
already served double duty as a subscript and as the complex unit. So an English language pun was introduced. The function
returns an m-by-n rectangular identity matrix and eye(n) returns an n-by-n square identity matrix.
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