Re: How to enter an integral in a formula and have mathematica *not*

*To*: mathgroup at smc.vnet.net*Subject*: [mg108993] Re: How to enter an integral in a formula and have mathematica *not**From*: "David Park" <djmpark at comcast.net>*Date*: Fri, 9 Apr 2010 03:33:43 -0400 (EDT)

You could use something like the following: f[x_] := x + HoldForm[Integrate[Sin[s + x], {s, 0, 1}]] f[.5] % /. Integrate -> NIntegrate // ReleaseHold The Presentations package has a Student's Integral section that allows one to hold integrals and manipulate them, using various integration techniques, before evaluation. One uses integrate with a small "i" and then later specifies the type of integration. f[x_] := x + integrate[Sin[s + x], {s, 0, 1}] f[.5] % // UseNIntegrate giving the same answers as above. David Park djmpark at comcast.net http://home.comcast.net/~djmpark/ From: Jim Rockford [mailto:jim.rockford1 at gmail.com] I have a certain integral, part of a larger expression, that can be expressed in terms of incomplete gamma functions by Mathematica. But in carrying out the definite integral and forcing it to be written in terms of gamma functions, this introduces branch points and other unnecessary complications. I want the integral left alone and evaluated numerically, but I still want to express the general formula for this large expression with the unevaluated integral in place. For example, I'd like f[x_] = (stuff) + int_{0}^{1} (g[s,x]) ds where the definite integral is expressed in the usual Mathematica notation. What I do *not* want Mathematica to do at this stage is to do the integral analytically and write it in terms of special functions. Instead, I just want to later make a list of values for f[x] and have the integral done numerically. How can I program this? Thanks, Jim