How I get area under the curve (AUC) value

Hello,

I am super bigginer at Matlab. I want to get AUC value only positive value.

which mean without Area over the curve value.

I using this code which I googled and learn from matlab Q&A. But this is for all area value.

>> D = readmatrix('F:\z-score.xlsx','Sheet','a','Range','B2:H50002');

>> t = D(1,:);

>> t = linspace(min(t), max(t), numel(t));

>> y1 = (D(6,:));

>> plot (t, y1);

>> area (t, y1);

>> polyarea (t,y1);

Thank you so much!

Answer 1

[Star Strider]

The file is not provided, however it is not absolutely necessary for this.

Try something like this —

D = 0.1*randn(6,12000)+(2*sin(6*pi*(0:11999)/11999));
t = linspace(0, 600, 12000);
y1 = D(6,:);
Lv = y1 >= 0;

AUc_pos = trapz(t(Lv),y1(Lv))

AUc_pos = 387.4466

figure
plot (t, y1);
hold on
patch([t(Lv) flip(t(Lv))], [zeros(size(y1(Lv))) flip(y1(Lv))], 'g', 'EdgeColor','g')
hold off

.

[Gyujin Park]

Wow, thank you so much!

Actually I read your previous comments and try to do but I couldn't so I put question my self.

But still not clear , I guess because I didn't attached my actual data.

Could you help me one more time with this data?

A is time for x, B is photometry data for y.

Thank you so much!

[Star Strider]

My pleasure!

Try this —

D = readtable('CNO(-).csv', 'VariableNamingRule','preserve')

D = 50001×2 table
    CNO (-)    GP_test1-230309-104013
    _______    ______________________

       -10            0.63836        
    -9.999            0.63818        
    -9.998            0.63787        
    -9.997            0.63747        
    -9.996            0.63722        
    -9.995            0.63703        
    -9.994            0.63671        
    -9.993            0.63643        
    -9.992            0.63623        
    -9.991            0.63593        
     -9.99            0.63555        
    -9.989            0.63529        
    -9.988            0.63514        
    -9.987            0.63485        
    -9.986            0.63468        
    -9.985            0.63449        

% D = sortrows(D,1)
VN = D.Properties.VariableNames;

t =  D{:,1};
y1 = D{:,2};

Lv = y1 >= 0;

AUC_pos = trapz(t(Lv),y1(Lv))

AUC_pos = 35.7356

figure
plot (t, y1);
hold on
patch([t(Lv); flip(t(Lv))], [zeros(size(y1(Lv))); flip(y1(Lv))], 'g', 'EdgeColor','g')
hold off
grid
xlabel(VN{1})
ylabel(strrep(VN{2},'_','\_'))
text(20.5, 2.6, sprintf('AUC = %9.5f',AUC_pos), 'Color','g', 'FontSize',12)

.

[Gyujin Park]

thank you so much!

very helpful code for me

[Star Strider]

As always, my pleasure!