How to calculate the area under the curve for each time gap using "trapz" command?

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Nadeera Gunartna
Nadeera Gunartna 2016-8-1
编辑： Stephen23 2016-8-2
I wanted to calculated the area under the curve of X vs T graph.
Here is the data set:
disp([T(:,5),X(:,5)])
1.00 2988.00
1.00 2966.00
1.00 2915.00
1.00 2891.00
1.00 2833.00
1.02 2846.00
1.19 2829.00
1.39 2799.00
1.66 2806.00
1.80 2804.00
2.00 2834.00
2.19 2827.00
2.39 2897.00
2.66 2889.00
2.80 2864.00
3.02 2874.00
3.19 2890.00
3.39 2874.00
3.64 2964.00
3.80 3059.00
4.02 3109.00
4.19 3214.00
4.39 3292.00
4.66 3334.00
4.80 3443.00
5.00 3515.00
5.19 3614.00
5.39 3736.00
5.66 3789.00
5.80 3811.00
6.00 3892.00
6.20 3954.00
6.41 3985.00
6.66 4039.00
6.80 4039.00
7.00 4045.00
7.19 4040.00
7.39 3977.00
7.66 3918.00
7.80 3961.00
8.02 3955.00
8.19 3923.00
8.39 3988.00
8.66 4064.00
8.80 4001.00
9.00 3991.00
9.19 4043.00
9.39 4021.00
9.66 3970.00
9.80 3967.00
10.00 3932.00
10.19 3856.00
10.39 3794.00
10.66 3782.00
10.80 3726.00
11.00 3688.00
11.19 3642.00
11.39 3584.00
11.66 3512.00
11.80 3398.00
12.02 3322.00
12.19 3222.00
12.39 3145.00
12.66 3098.00
12.80 3144.00
13.02 3134.00
13.19 3137.00
13.41 3175.00
13.64 3152.00
13.80 3095.00
14.02 3062.00
14.19 3046.00
14.39 3010.00
then I used "trapz" command to calculate the area under the curve.
totalcounts=trapz(T(:,5),X(:,5))
But, now I need to calculate the area under the curve for each time period ( for each time gap). I would be greatful, if anyone can guide me.
Thanks in advance.

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采纳的回答

Torsten
Torsten 2016-8-1
area(1:N-1)=0.5*(X(1:N-1,5))+X(2:N,5))*(T(2:N,5)-T(1:N-1,5))
Best wishes
Torsten.
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Torsten
Torsten 2016-8-2
编辑：Torsten 2016-8-2
Should read:
N=size(T,1);
area(1:N-1)=0.5*(X(1:N-1,5)+X(2:N,5)).*(T(2:N,5)-T(1:N-1,5))
Sorry.
Best wishes
Torsten.

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