why i

[Peter Hansen]

Richard Brodie wrote:

> "Peter Hansen" <peter at engcorp.com> wrote in message news:N9KdnVD1v92IlS7d4p2dnA at powergate.ca...
>>The idea that 'i' is mnemonic for 'integer' is interesting, though.
>>If the mathematical field is really the origin, rather than FORTRAN,
>>it would be interesting to know if that was how "they" picked it.
>>
>>Googling to little avail, the best I could find to help was Hilbert's
>>1900 address on "23 Mathematical Problems" which he gave to the Int'l
>>Congress of Mathematics in Paris, proving a usage which predates
>>FORTRAN by 50-some years.
> 
> I would assume vector algeba was the origin; Google can go back
> to 1843 on that line:  http://www.wordiq.com/definition/Quaternion
> 
> That suggests that i, j, k notation is an extension of complex notation
> so i must be the Euler i (1777) presumably standing for imaginary.

I'm not sure we should consider that early usage to be of
the same type.  The Hilbert usage is as a subscript, which
corresponds to (I think) the reason for using i,j,k as indices
in a program loop: to index into a vector, as in M[i] and such.

-Peter