Re: NestList integration bug?
- To: mathgroup at smc.vnet.net
- Subject: [mg117537] Re: NestList integration bug?
- From: Szabolcs Horvát <szhorvat at gmail.com>
- Date: Tue, 22 Mar 2011 05:06:41 -0500 (EST)
- References: <im7c40$4h$1@smc.vnet.net>
On 2011.03.21. 12:17, Jon Joseph wrote:
> All: Please comment on the following code:
>
> The following input: NestList[Integrate[#, {t, a, x }]&, m, 5]
> (* m is a constant *)
>
> results in {m, m(-a + x), m (-a + x)^2, m (-a + x)^3, m (-a + x)^4, m
> (-a + x)^5}
>
> which is missing the divisors as a result of the integration. However,
> doing the integral indefinitely:
>
> NestList[Integrate[#, x]&, m, 5] results in
>
>
> {m, m x, (m x^2)/2, (m x^3)/6, (m x^4)/24, (m x^5)/120}
>
> which is correct.
>
> What am I missing?
>
First you are integrating an expression that contains no t with respect
to t.
In[1]:= Integrate[m, {t, a, x}]
Out[1]= m (-a + x)
In[2]:= Integrate[%, {t, a, x}]
Out[2]= m (-a + x)^2
In[3]:= Integrate[%, {t, a, x}]
Out[3]= m (-a + x)^3
Then you are integrating with respect to x.
Perhaps you meant NestList[Integrate[#, {x, 0, x}] &, m, 5]