Unspecified behaviour of function imag.

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In version '9.10.0.1602886 (R2021a)', running
imag part
ans = 1×4
0 0 0 0
will return
[0 0 0 0]
ans = 1×4
0 0 0 0
I accidentally found this when trying to type "imagpart". How does this happen? Will it affect our program in other unanticipated ways?

Accepted Answer

Walter Roberson
Walter Roberson on 30 Nov 2021
This will not affect your code.
When you call
imag part
that is the same as if you had invoked
imag('part')
which is calling imag() on the vector of four characters, 'p', 'a', 'r', 't' .
In many circumstances, characters automatically convert to the numeric codes used to internally encode the characters, such as 112 for 'p', and 97 for 'a' . So imag() treats this as a vector of real-valued double precision numbers. But the imaginary() portion of those is all 0 so 0 0 0 0 gets returned.

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