How can I calculate the areas between these two curves?

Question

Jose Aroca 2020-7-15

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https://ww2.mathworks.cn/matlabcentral/answers/565508-how-can-i-calculate-the-areas-between-these-two-curves

评论： Jose Aroca 2020-7-26

I need to calculate both areas A and B that lie between these two curves. The curves are extracted form two text files, which are attatched. The code below shows how the graph is produced.

close all
clearvars
DM = readtable('FF677-Di01.txt');
plot (DM{:,1},DM{:,2})
hold on
AF = readtable('Alexa Fluor 647 - Em.txt');
plot (AF{:,1},AF{:,2})
A = intersect(DM{:,1}, AF{:,1});
xlim ([500 900])
hold on
AArea = trapz(AF{:,1},AF{:,2});
DMArea = trapz(DM{:,1},DM{:,2});

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Answer 1

Dinesh Yadav 2020-7-22

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/565508-how-can-i-calculate-the-areas-between-these-two-curves#answer_469170

在 MATLAB Online 中打开

To calculate the area B change the follwing line of code

AArea = trapz(AF{:,1},AF{:,2});

to

AArea = abs(trapz(AF{:,1},(AF{:,2} - DM{:,2} )));

and to compute area A calculate the area under the AF and subtract AArea from it

DMArea = abs(trapz(AF1{:,1},AF{:,2} - AArea);

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Jose Aroca 2020-7-26

Hi. First of allm thank you for your answer. I have tried adding your suggestions but I don't think I get the correct answer. I get an area for B of about 490, when it should be about 20.5, and therefore the area calculated for A is also wrong. I am not sure how to correct this.

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