cleaning experimental data, finding the surface of the peaks in some measures

hello everybody, i am working with some graph of measures of a photomultiplicator and i measure the values of luminicens, the problem i have is that the photomultiplicator it detects, the light of some particules and the light of a lamp and this one isnt a constant value (sometimes it increase sometimes it decreas) and because i need to calculate de area(as it shows in the picture) of the peak, to relate it with the concentration of the particules, i am strugeling to find anything that could do that work automatically ( i have more than 50 measures each time). for cleaning the signal i use the comand sgolayfilt (it gives me the green curve) and i would like to calculate the area in black

i have found something that it would help baseline fit but it doesnt find the points (where to begin and where to end of the black line) by itself... and doenst calculate the area eighter, (in case that i find a way to have the points of the black line it wouldnt be difficult to calculate)

Answer 1

[KSSV]

doc trapz

Also check the link: https://in.mathworks.com/matlabcentral/answers/154089-area-under-curve-no-function

[franco otaola]

i already calculated the area of all the curve,and i used trapz like in the link you post it

if i could take a constant value for the signal of the lamp everything would be okay because i could calculate the two of them and calculate the real area like realArea=areaofCurve-constant*deltaX, but sometimes the difference between the firsts and the lasts measures are really different (so the begin and the end of the peak are not at the same level, like in the first image, the black line sometimes is horizontal, sometimes not, that’s why i need to find the points where the peak begins and ends) and i can’t take a the middle value between them.