Gamma function
08-06-2020, 01:56 PM
Post: #1
 robmio Junior Member Posts: 25 Joined: Jan 2020
Gamma function
Hello everyone, I would like to know how to replace "Gamma(a,0)" and "Gamma(a,infinity)" ("a" equal, for example, to 2, or to 1/5, etc.) with "gamma(a)" and with "0" , respectively.
For example the following approach does not work:

"subst(Gamma (2/3,0), Gamma (a,0), Gamma(a))".

How can I do?
Sincerely, robmio
08-06-2020, 03:49 PM
Post: #2
 robmio Junior Member Posts: 25 Joined: Jan 2020
RE: Gamma function
For example: laplace(t^(-1/3),t,s) -->
(-s*Gamma(2/3,infinity)+s*Gamma(2/3,0))/(s*(s^(2/3))).
08-06-2020, 05:17 PM (This post was last modified: 08-06-2020 05:59 PM by Major.)
Post: #3
 Major Junior Member Posts: 21 Joined: Jan 2020
RE: Gamma function
From what I see the Gamma function only takes one argument unless I am missing something.

EDIT: Oh I see it outputs that as an answer

I know you can change the expression to a string (STRING) and use the replace (REPLACE) command, but afterwards I am unsure because I do not know how to convert the string back to an expression.

There may or may not be a function to change a string into an unsolved expression, but I can't find it. Hopefully someone can help you.

But if you want to solve it you can use EXPR.

Control System Programs
08-06-2020, 06:14 PM
Post: #4
 robmio Junior Member Posts: 25 Joined: Jan 2020
RE: Gamma function
In HP PRIME, Gamma function can take one argument as "complete" gamma function, or 2 arguments as incomplete gamma function:

Gamma(a) = Gamma(a,0) = int(t^(a-1)*exp(-t),t,0,infinity)

Gamma(a,x) = int(t^(a-1)*exp(-t),t,x,infinity).

In HP PRIME, for example, Gamma(0.5,0) = 1.7724
Gamma(0.5,2) = 0.080647.
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