[Scilab-users] Si function

[Samuel Gougeon]

Le 06/02/2020 à 10:41, Federico Miyara a écrit :
>
> Dear All,
>
> Just in case somebody is interested, find attached a Scilab function 
> to compute the sine integral function Si (the integral from 0 to x of 
> the sinc function), which cannot be expressed in closed form with 
> elementary functions.
>
> /It is preliminary, it doesn't test for appropriate input argument.
>
> It works for real or complex matrices or N-D arrays.
>
> It can be easily modified to get the cosine integral function.
> /

Great work, Federico! Just a comment: IMHO, so short functions names 
should really be avoided.
The shorter the name, the more probable are collisions with other users 
common variables.

By the way, i am wondering about a similar expint() function = integral 
of dt*exp(t)/t.

 From there, the linearity of the integration operator and the Euler 
formula would yield
in a trivial way sinint(a) and cosint(a), with a (almost) one-line 
definition using
expint([-a a]*%i).

Wouldn't they?

Best regards
Samuel

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