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[求助] MATLAB一個(gè)數(shù)值積分的問(wèn)題

待求參數(shù)an如附件中的公式所示，θ∈[0,2π]，由于公式中的D(θ)是以區(qū)間[0,2π]上均勻的離散的144個(gè)點(diǎn)的形式給出的：
D=[2.524,2.522,2.518,2.512,2.504,2.495,2.484,2.472,2.459,2.444,2.427,2.41,2.391,2.372,...
2.351,2.329,2.305,2.281,2.256,2.229,2.201,2.172,2.142,2.111,2.079,...
2.046,2.011,1.975,1.938,1.9,1.86,1.82,1.778,1.735,1.69,1.645,1.598,...
1.55,1.501,1.451,1.399,1.347,1.294,1.239,1.184,1.129,1.072,1.015,...
0.958,0.901,0.844,0.786,0.729,0.673,0.618,0.563,0.51,0.459,0.409,...
0.361,0.315,0.272,0.231,0.193,0.158,0.127,0.098,0.074,0.052,0.034,...
0.02,0.01,0.003,0,0,0.004,0.012,0.023,0.037,0.054,0.074,0.097,0.123,...
0.152,0.183,0.216,0.251,0.289,0.328,0.369,0.412,0.456,0.501,0.548,...
0.596,0.645,0.694,0.745,0.797,0.849,0.901,0.954,1.008,1.062,1.116,...
1.17,1.225,1.279,1.334,1.388,1.442,1.496,1.55,1.603,1.655,1.707,1.758,...
1.808,1.858,1.906,1.953,1.999,2.043,2.086,2.127,2.167,2.205,2.241,...
2.275,2.307,2.337,2.365,2.391,2.414,2.435,2.454,2.471,2.485,2.497,...
2.507,2.515,2.52,2.524,2.525];

  所以只能求得數(shù)值積分。
  我的求解程序如下：
  b=linspace(0,2*pi,144);
  for n=1:300
for i=1:144
c(i)=D(i)*cos(n*(i-1)*2*pi/143);
end
a(n)=1/pi*trapz(b,c)
end

請(qǐng)問(wèn)我這個(gè)程序?qū)幔咳绻粚?duì)，求正確的！
  請(qǐng)大家?guī)蛶兔�，在輸入原始�?shù)據(jù)D的時(shí)候，直接在我這里復(fù)制可以了哈！

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倚樓聽(tīng)風(fēng)雨，淡看江湖路

1樓 2012-09-25 21:42:19

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★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★
感謝參與，應(yīng)助指數(shù) +1
dbb627: 金幣+1, 感謝應(yīng)助 2012-09-26 21:06:30
apollosun9283: 金幣+30, ★★★很有幫助 2012-10-15 10:11:14

clear;clc
D=[2.524,2.522,2.518,2.512,2.504,2.495,2.484,2.472,2.459,2.444,2.427,2.41,2.391,2.372,...
2.351,2.329,2.305,2.281,2.256,2.229,2.201,2.172,2.142,2.111,2.079,...
2.046,2.011,1.975,1.938,1.9,1.86,1.82,1.778,1.735,1.69,1.645,1.598,...
1.55,1.501,1.451,1.399,1.347,1.294,1.239,1.184,1.129,1.072,1.015,...
0.958,0.901,0.844,0.786,0.729,0.673,0.618,0.563,0.51,0.459,0.409,...
0.361,0.315,0.272,0.231,0.193,0.158,0.127,0.098,0.074,0.052,0.034,...
0.02,0.01,0.003,0,0,0.004,0.012,0.023,0.037,0.054,0.074,0.097,0.123,...
0.152,0.183,0.216,0.251,0.289,0.328,0.369,0.412,0.456,0.501,0.548,...
0.596,0.645,0.694,0.745,0.797,0.849,0.901,0.954,1.008,1.062,1.116,...
1.17,1.225,1.279,1.334,1.388,1.442,1.496,1.55,1.603,1.655,1.707,1.758,...
1.808,1.858,1.906,1.953,1.999,2.043,2.086,2.127,2.167,2.205,2.241,...
2.275,2.307,2.337,2.365,2.391,2.414,2.435,2.454,2.471,2.485,2.497,...
2.507,2.515,2.52,2.524,2.525];

  for n=1:300
   X=linspace(0,2*n*pi,144);
   Y=D.*cos(n*X);
   Z(n)=trapz(X,Y);
  end

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我不管是否能夠贏得成功，既然選擇了遠(yuǎn)方，便只顧風(fēng)雨兼程！

3樓2012-09-26 09:37:04

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感謝參與，應(yīng)助指數(shù) +1

來(lái)給你添點(diǎn)人氣，我是化工的，學(xué)過(guò)Matlab，但是還是有待繼續(xù)努力啊

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開(kāi)心就好！

2樓2012-09-26 08:35:02

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月只藍(lán)

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dbb627: 金幣+1, 謝謝應(yīng)助！ 2012-09-26 21:05:49

引用回帖:

3樓: Originally posted by 328911052 at 2012-09-26 09:37:04
clear;clc
D=;

  for n=1:300
   X=linspace(0,2*n*pi,144);
   Y=D.*cos(n*X);
   Z(n)=trapz(X,Y);
  end...

感謝您的參與！
您的程序和我的其實(shí)是一樣的。
不過(guò)，您在算cos(nθ)的時(shí)候，積分上下限取的是[0，2nπ]，是不是取錯(cuò)了，應(yīng)該是[0，2π]。
此外，最后在調(diào)用梯形積分函數(shù)trapz的時(shí)候，您好像漏掉了1/π。
我在您程序上作了上述修改后，我算出的a和您程序算出的Z，吻合得很好。

untitled.jpg

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MATLAB、MS小問(wèn)題、普通問(wèn)題請(qǐng)發(fā)帖求助！時(shí)間精力有限，恕不接受無(wú)償私信求助。

4樓2012-09-26 10:44:15

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huwanpeng2

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感謝參與，應(yīng)助指數(shù) +1

建議參考黃華江的那本書(shū)，化學(xué)工業(yè)出版社，有例子的

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skloche.ecust

5樓2012-09-26 11:02:13

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