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

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.

Answer 1

[Torsten]

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.

[Nadeera Gunartna]

I tried this,but it does not show anything as a result.

i=1:1:length(T(:,5));

for j=1:i-1

A(j)=0.5*((X(i,5)+X(i+1,5))*(T(i+1,5)-T(i,5)))

disp(A(j))

end

and I tried this one too

A(1:i-1)=0.5*((X(i,5)+X(i+1,5))*(T(i+1,5)-T(i,5)))

then it shows me 'Index exceeds matrix dimensions.'

[Torsten]

Why don't you just execute my command line ?

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))

Best wishes

Torsten.

[Torsten]

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.

[Nadeera Gunartna]

Thanks for the kind help