Subject: RE: Using the Normal Distribution in Maxima
From: Robert Dodier
Date: Wed, 7 Sep 2005 07:54:23 -0600
hello tolga,
> Can I do the following:
>
> - define a function myself, just simply called N(x)
> - tell Maxima that dN=n, i.e. that if it encounters N during differentiation,
> it should just return n
> - and then differentiate as below
>
> Maxima doesn't have to know what N is (i.e. for example that
> N(x)=1/2 erf(x/sqrt(2)) .
you can use the gradef function to define the derivative of N ...
(%i1) gradef (N(x), dN(x));
(%o1) N(x)
(%i2) diff (N(f(x)), x);
(%o2) dN(f(x))*'diff(f(x),x,1)
it is not necessary to define N before using it in an expression.
if at some later stage you want to substitute the definition of dN,
you could do dN (x) := exp (-x^2/2)/sqrt(2 * %pi); ''%o2;
(note the presence of two single quote marks '' in front of %o2 --
that means to re-evaluate %o2.)
hope this helps,
robert dodier