Re: Bug in NIntegrate[]?

*To*: mathgroup at smc.vnet.net*Subject*: [mg126887] Re: Bug in NIntegrate[]?*From*: Gerry Flanagan <gvflan at midcoast.com>*Date*: Fri, 15 Jun 2012 15:27:46 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <201206150741.DAA24405@smc.vnet.net>

Good reason to use Piecewise f[x_] := Piecewise[{{0, x < 0 || x > 1}, {1, True}}] Integrates correctly. Gerry F. On 6/15/2012 3:41 AM, GS wrote: > I define the function f[x] as follows: > > f[x_] := 0 /; x< 0 || x> 1; > f[x_] := 1 > > It is zero outside of the interval [0,1]. This can be verified by plotting > Plot[f[x], {x, -1, 2}] > > Now I integrate it from -1 to 2: > In[270]:= NIntegrate[f[x], {x, -1, 2}] > Out[270]= 3. > > The result should be 1, but it is 3. Clearly Mathematica ignores the fact that f[x] is zero outside of [0,1]. > > This caused a lot of headache for me recently when I encountered such behavior in one of my research code. > GS > > >

**References**:**Bug in NIntegrate[]?***From:*GS <vokaputs@gmail.com>