area between a curve and a linear function

Hi guys and girls,

I have x & y data for a curve. I want to calculate the area under the curve. So i generated a linear function as "downwards-limit".

I tried to use the trapz() function;

area_between_curves = trapz([Temparea,DSC],abs([gerade_punkt1,gerade_punkt2]-[Temparea,DSC]));

but i didn't manage to make it work...

A1 = readmatrix("Data_neu.txt");
Temp = A1(:,1); %[°C]
%Time = A1(:,2); %[min]
DSC = A1(:,3); %[mW/mg]
%Sensit = A1(:,4); %[uV/mW]
%Segment = A1(:,5);
gerade_punkt1 = [227.278,248.0764]; %[227.278,2.5461]; 
gerade_punkt2 = [2.5461,2.778]; %[244.423,2.7609];
%
Temparea = Temp(1017:1120,1);
DSCarea = DSC(1017:1120,1);
%plot
figure("Name","heat fusion")
hold on
plot(Temparea,DSCarea)
plot(gerade_punkt1,gerade_punkt2)
grid on
hold off

Thanks a lot!

Answer 1

[Voss]

y_downwards_limit = linspace(gerade_punkt2(1),gerade_punkt2(2),numel(Temparea)).';

area_between_curves = trapz(Temparea, DSCarea-y_downwards_limit)

[Voss]

A1 = readmatrix("Data_neu.txt");

Temp = A1(:,1); %[°C]
DSC  = A1(:,3); %[mW/mg]

start_idx = 1017;
end_idx   = 1120;

Temparea = Temp(start_idx:end_idx,1);
DSCarea  = DSC(start_idx:end_idx,1);

%plot
figure("Name","heat fusion")
hold on
plot(Temparea,DSCarea)
plot(Temparea([1,end]),DSCarea([1,end]))
grid on
hold off

y_downwards_limit = linspace(DSCarea(1),DSCarea(end),end_idx-start_idx+1).';

area_between_curves = trapz(Temparea, DSCarea-y_downwards_limit)

area_between_curves = 11.1183