level 9
龙化要元
楼主
使用数值积分时候出现问题了,因为函数比较复杂,用Integrate耗时很长,用NIntegrate是不是时间短一点啊?但是问题来了,数值积分有时得不到结果,举个例子如下
Integrate[(5.25328 - x)^(0.23 - 1), x];
Integrate[(5.25328 - x)^(0.23 - 1), {x, 0, 5.25328}];
NIntegrate[(5.25328 - x)^(0.23 - 1), {x, 0, 5.25328}];
第一个能得到积分式子,第二个给出定积分数值,
第三个NIntegrate::zeroregion: Integration region {{5.25328,5.25328000000000017166712495949706583
13315518215
3581063474170620791}} cannot be further subdivided at the specified working precision. NIntegrate assumes zero integral there and on any further indivisible regions. >>NIntegrate::inumri: The integrand 1/(5.25328 -x)^0.77 has evaluated to Overflow, Indeterminate, or Infinity for all sampling points in the region with boundaries {{5.25328000000000017166712495949706583
13315518215
3581063474170620791,5.25328000000000017140366952968504617598149925854586194160721553198}}. >>
我的区间{0,5.25328},为什么它给弄个小区间{5.25328,5.2532800……1716……}且在这上面值超过范围了,怎么样才能让NIntegrate算出Integrate相同或者相近的结果而不是报错啊?谢谢啦。
2015年01月06日 09点01分
1
Integrate[(5.25328 - x)^(0.23 - 1), x];
Integrate[(5.25328 - x)^(0.23 - 1), {x, 0, 5.25328}];
NIntegrate[(5.25328 - x)^(0.23 - 1), {x, 0, 5.25328}];
第一个能得到积分式子,第二个给出定积分数值,
第三个NIntegrate::zeroregion: Integration region {{5.25328,5.25328000000000017166712495949706583
13315518215
3581063474170620791}} cannot be further subdivided at the specified working precision. NIntegrate assumes zero integral there and on any further indivisible regions. >>NIntegrate::inumri: The integrand 1/(5.25328 -x)^0.77 has evaluated to Overflow, Indeterminate, or Infinity for all sampling points in the region with boundaries {{5.25328000000000017166712495949706583
13315518215
3581063474170620791,5.25328000000000017140366952968504617598149925854586194160721553198}}. >>
我的区间{0,5.25328},为什么它给弄个小区间{5.25328,5.2532800……1716……}且在这上面值超过范围了,怎么样才能让NIntegrate算出Integrate相同或者相近的结果而不是报错啊?谢谢啦。

