Using different baselines to estimate area of two peaks

Question

I have the following data:

data = {{66.803, 0.0592517}, {66.836, 0.0591485}, {66.87, 0.058002}, {66.904, 0.0569173}, {66.937, 0.0570737}, {66.97, 0.0570687}, {67.003, 0.0572252}, {67.036, 0.0573801}, {67.068, 0.0577948}, {67.102, 0.0577485}, {67.135, 0.0577799}, {67.168, 0.0581311}, {67.201, 0.058161}, {67.234, 0.0583523}, {67.268, 0.0583076}, {67.301, 0.0584974}, {67.334, 0.0585288}, {67.368, 0.0581627}, {67.4, 0.0584285}, {67.433, 0.0584568}, {67.467, 0.0582475}, {67.5, 0.0582757}, {67.532, 0.05854}, {67.565, 0.0585698}, {67.598, 0.0585997}, {67.631, 0.0584712}, {67.664, 0.0586625}, {67.698, 0.0584563}, {67.731, 0.0582883}, {67.764, 0.0580917}, {67.796, 0.0582942}, {67.829, 0.0580977}, {67.863, 0.0578235}, {67.896, 0.0577852}, {67.93, 0.0573464}, {67.963, 0.0573065}, {67.996, 0.0572651}, {68.029, 0.0570654}, {68.062, 0.0571538}, {68.095, 0.0573135}, {68.128, 0.0573148}, {68.161, 0.0574761}, {68.194, 0.0576357}, {68.227, 0.0577004}, {68.261, 0.0574547}, {68.293, 0.0576841}, {68.326, 0.0576759}, {68.359, 0.0576677}, {68.392, 0.0577419}, {68.426, 0.0576339}, {68.459, 0.0577603}, {68.492, 0.0578867}, {68.525, 0.0580131}, {68.558, 0.0581791}, {68.591, 0.058209}, {68.624, 0.0583987}, {68.657, 0.0585884}, {68.69, 0.0587781}, {68.723, 0.0589489}, {68.756, 0.0589455}, {68.788, 0.0593332}, {68.821, 0.0594897}, {68.855, 0.0594118}, {68.888, 0.0597297}, {68.921, 0.0598878}, {68.954, 0.0600459}, {68.987, 0.0602039}, {69.02, 0.060362}, {69.053, 0.0605185}, {69.086, 0.0608349}, {69.119, 0.0609898}, {69.152, 0.0611463}, {69.185, 0.0613012}, {69.218, 0.0616191}, {69.252, 0.0615444}, {69.285, 0.0618623}, {69.318, 0.0620204}, {69.351, 0.0621785}, {69.384, 0.06246}, {69.417, 0.0625516}, {69.45, 0.0626448}, {69.484, 0.0625004}, {69.517, 0.0625919}, {69.551, 0.0625077}, {69.584, 0.0628557}, {69.617, 0.0630423}, {69.65, 0.0632304}, {69.683, 0.0634186}, {69.716, 0.0636083}, {69.749, 0.063798}, {69.781, 0.064219}, {69.815, 0.0641775}, {69.848, 0.0643672}, {69.881, 0.0647169}, {69.914, 0.0649034}, {69.947, 0.0650916}, {69.981, 0.0650469}, {70.014, 0.0652351}, {70.048, 0.065412}, {70.08, 0.0659248}, {70.113, 0.0662079}, {70.146, 0.0666526}, {70.179, 0.0669357}, {70.211, 0.0675735}, {70.245, 0.0677236}, {70.278, 0.0681065}, {70.311, 0.0683279}, {70.345, 0.0684795}, {70.378, 0.0689399}, {70.41, 0.0694242}, {70.443, 0.0696725}, {70.476, 0.0700807}, {70.509, 0.0703306}, {70.542, 0.0706581}, {70.576, 0.0709664}, {70.609, 0.0713477}, {70.641, 0.072117}, {70.674, 0.0724967}, {70.707, 0.0729983}, {70.74, 0.0733147}, {70.773, 0.0737894}, {70.807, 0.0738729}, {70.84, 0.0743492}, {70.873, 0.0748017}, {70.905, 0.0754776}, {70.938, 0.0759174}, {70.971, 0.0763589}, {71.004, 0.0768003}, {71.037, 0.0770851}, {71.071, 0.0772968}, {71.104, 0.077743}, {71.136, 0.0784236}, {71.17, 0.0787969}, {71.202, 0.0794364}, {71.235, 0.0798161}, {71.268, 0.0801958}, {71.301, 0.0807354}, {71.335, 0.0808791}, {71.368, 0.0813759}, {71.401, 0.081849}, {71.434, 0.0823206}, {71.467, 0.0827937}, {71.5, 0.0832652}, {71.533, 0.0837842}, {71.566, 0.084327}, {71.6, 0.0847952}, {71.632, 0.085574}, {71.665, 0.0862767}, {71.698, 0.0869382}, {71.731, 0.0874176}, {71.764, 0.0880569}, {71.797, 0.0885364}, {71.831, 0.0889381}, {71.864, 0.0895316}, {71.897, 0.0900997}, {71.93, 0.0906677}, {71.962, 0.0916349}, {71.995, 0.092203}, {72.028, 0.0929959}, {72.061, 0.0936669}, {72.094, 0.0944994}, {72.128, 0.0950927}, {72.161, 0.0959236}, {72.194, 0.0967117}, {72.226, 0.0977153}, {72.259, 0.0984781}, {72.292, 0.0992425}, {72.326, 0.0997677}, {72.359, 0.100592}, {72.392, 0.101612}, {72.424, 0.102709}, {72.458, 0.103492}, {72.491, 0.104351}, {72.524, 0.105329}, {72.557, 0.106281}, {72.59, 0.107233}, {72.623, 0.108186}, {72.656, 0.109137}, {72.688, 0.110454}, {72.722, 0.111212}, {72.754, 0.112434}, {72.787, 0.113425}, {72.821, 0.114023}, {72.854, 0.115609}, {72.887, 0.11701}, {72.919, 0.118166}, {72.952, 0.119087}, {72.985, 0.120647}, {73.019, 0.121519}, {73.052, 0.122638}, {73.085, 0.124236}, {73.118, 0.125355}, {73.152, 0.126241}, {73.184, 0.12771}, {73.217, 0.128761}, {73.249, 0.130048}, {73.282, 0.1311}, {73.315, 0.132311}, {73.348, 0.133561}, {73.382, 0.134444}, {73.415, 0.136361}, {73.448, 0.138117}, {73.481, 0.139392}, {73.514, 0.14127}, {73.547, 0.142484}, {73.58, 0.143859}, {73.613, 0.145075}, {73.647, 0.146214}, {73.679, 0.147801}, {73.712, 0.149138}, {73.745, 0.150314}, {73.778, 0.151652}, {73.811, 0.153147}, {73.844, 0.154569}, {73.878, 0.155968}, {73.911, 0.157598}, {73.944, 0.160028}, {73.977, 0.161818}, {74.01, 0.163267}, {74.042, 0.165097}, {74.075, 0.166852}, {74.109, 0.168215}, {74.142, 0.16981}, {74.176, 0.171334}, {74.209, 0.17341}, {74.241, 0.175559}, {74.274, 0.178596}, {74.307, 0.180671}, {74.34, 0.183791}, {74.373, 0.185997}, {74.407, 0.188137}, {74.44, 0.191785}, {74.473, 0.194151}, {74.506, 0.19644}, {74.539, 0.198997}, {74.572, 0.201552}, {74.605, 0.204268}, {74.638, 0.208585}, {74.671, 0.21142}, {74.705, 0.214154}, {74.738, 0.217443}, {74.771, 0.220733}, {74.804, 0.225942}, {74.837, 0.229501}, {74.87, 0.233596}, {74.904, 0.239381}, {74.937, 0.243794}, {74.97, 0.250129}, {75.003, 0.254638}, {75.036, 0.259594}, {75.069, 0.266791}, {75.102, 0.272708}, {75.135, 0.280225}, {75.168, 0.286304}, {75.201, 0.294463}, {75.233, 0.301094}, {75.266, 0.309735}, {75.3, 0.316702}, {75.333, 0.324539}, {75.366, 0.332695}, {75.4, 0.3427}, {75.433, 0.352938}, {75.466, 0.363334}, {75.499, 0.373573}, {75.531, 0.383886}, {75.564, 0.392686}, {75.597, 0.400206}, {75.63, 0.405805}, {75.663, 0.414404}, {75.697, 0.423062}, {75.73, 0.432275}, {75.762, 0.441723}, {75.795, 0.450937}, {75.828, 0.460329}, {75.861, 0.469574}, {75.894, 0.478018}, {75.927, 0.485343}, {75.961, 0.491474}, {75.994, 0.495995}, {76.027, 0.497268}, {76.06, 0.490378}, {76.093, 0.48685}, {76.125, 0.474117}, {76.159, 0.465758}, {76.192, 0.454619}, {76.225, 0.432919}, {76.258, 0.414738}, {76.291, 0.391278}, {76.324, 0.368156}, {76.357, 0.344888}, {76.39, 0.323379}, {76.423, 0.303791}, {76.456, 0.286443}, {76.489, 0.271034}, {76.522, 0.250037}, {76.556, 0.229126}, {76.589, 0.209889}, {76.622, 0.191613}, {76.655, 0.175856}, {76.689, 0.166238}, {76.722, 0.153977}, {76.755, 0.146995}, {76.788, 0.141294}, {76.821, 0.132634}, {76.853, 0.128412}, {76.886, 0.12476}, {76.919, 0.121907}, {76.952, 0.118894}, {76.985, 0.11618}, {77.018, 0.113294}, {77.051, 0.110726}, {77.084, 0.105919}, {77.117, 0.103671}, {77.151, 0.101397}, {77.184, 0.100018}, {77.217, 0.0965602}, {77.25, 0.0955008}, {77.284, 0.0943717}, {77.316, 0.0920634}, {77.349, 0.0911022}, {77.382, 0.0904608}, {77.415, 0.0899777}, {77.448, 0.0891764}, {77.481, 0.0883735}, {77.515, 0.0873346}, {77.548, 0.0866917}, {77.581, 0.0857257}, {77.614, 0.0846015}, {77.647, 0.0837004}, {77.68, 0.0826759}, {77.713, 0.0818113}, {77.746, 0.0811066}, {77.779, 0.0804018}, {77.812, 0.0797161}, {77.845, 0.079043}, {77.878, 0.0782101}, {77.911, 0.077537}, {77.944, 0.0770238}, {77.977, 0.0758204}, {78.01, 0.0752075}, {78.043, 0.0747545}, {78.076, 0.0741432}, {78.109, 0.0733704}, {78.142, 0.0727923}, {78.176, 0.0720162}, {78.209, 0.0716297}, {78.243, 0.0706922}, {78.276, 0.0701458}, {78.309, 0.0690658}, {78.342, 0.068741}, {78.374, 0.0680095}, {78.407, 0.0675264}, {78.44, 0.0670417}, {78.473, 0.0665729}, {78.506, 0.0661215}, {78.539, 0.0653487}, {78.572, 0.0650555}, {78.605, 0.064764}, {78.638, 0.0644709}, {78.67, 0.0645705}, {78.703, 0.0641191}, {78.737, 0.0635947}, {78.77, 0.0634615}, {78.803, 0.0629942}, {78.836, 0.0623528}, {78.868, 0.0621041}, {78.901, 0.061621}, {78.934, 0.0611395}, {78.967, 0.0607878}, {79.001, 0.0600038}, {79.034, 0.0596157}, {79.067, 0.0592276}, {79.1, 0.0588395}, {79.133, 0.0585448}, {79.167, 0.0581218}, {79.199, 0.0581549}, {79.232, 0.0579615}, {79.265, 0.0577665}, {79.298, 0.0577172}, {79.331, 0.0574874}, {79.364, 0.0572592}, {79.397, 0.057031}, {79.43, 0.0569627}, {79.463, 0.0566902}, {79.497, 0.0561294}, {79.529, 0.0560358}, {79.562, 0.0557095}, {79.595, 0.055543}, {79.628, 0.0552483}, {79.66, 0.0552181}, {79.694, 0.0548869}, {79.727, 0.054627}, {79.76, 0.054527}, {79.794, 0.0539853}, {79.827, 0.0537887}, {79.86, 0.0535922}, {79.893, 0.0532357}, {79.926, 0.0530408}, {79.959, 0.0526669}, {79.993, 0.0522043}, {80.026, 0.0519761}, {80.06, 0.0515119}, {80.093, 0.0514436}, {80.125, 0.0514513}, {80.159, 0.0509871}, {80.191, 0.0511532}, {80.224, 0.050925}, {80.258, 0.0504624}, {80.29, 0.0504512}, {80.324, 0.0501152}, {80.357, 0.0498553}, {80.39, 0.0497538}, {80.423, 0.0494939}, {80.456, 0.0492166}, {80.489, 0.0490881}, {80.522, 0.0487998}, {80.556, 0.0484337}, {80.588, 0.0485412}, {80.622, 0.048172}, {80.655, 0.0478757}, {80.687, 0.0479769}, {80.72, 0.0478405}, {80.753, 0.0475458}, {80.786, 0.0472717}, {80.819, 0.0471749}, {80.852, 0.0470781}, {80.885, 0.0468198}, {80.918, 0.046723}, {80.951, 0.0466072}, {80.984, 0.0464739}, {81.017, 0.0461824}, {81.049, 0.0462868}, {81.082, 0.0461535}, {81.116, 0.0456403}, {81.149, 0.0453772}, {81.181, 0.0455101}, {81.215, 0.0450095}, {81.248, 0.0449063}, {81.281, 0.0446828}, {81.314, 0.0446494}, {81.348, 0.0442232}, {81.381, 0.0440282}, {81.414, 0.0438348}, {81.446, 0.0438742}, {81.479, 0.0436777}, {81.513, 0.0434066}, {81.546, 0.0433716}, {81.579, 0.0433349}, {81.612, 0.0432112}, {81.645, 0.0433043}, {81.678, 0.043236}, {81.71, 0.0435573}, {81.743, 0.0434889}, {81.776, 0.043438}, {81.81, 0.0431717}, {81.843, 0.0431367}, {81.875, 0.0433281}, {81.909, 0.0430634}, {81.942, 0.0430077}, {81.975, 0.0429378}, {82.007, 0.0430976}, {82.04, 0.0430261}, {82.073, 0.0429562}, {82.106, 0.0430842}, {82.14, 0.0428511}, {82.173, 0.0428477}, {82.206, 0.0428427}, {82.239, 0.0429992}, {82.271, 0.0432413}, {82.304, 0.0432711}, {82.337, 0.0434593}, {82.37, 0.0434891}, {82.403, 0.0436772}, {82.437, 0.0433856}, {82.47, 0.0432508}, {82.503, 0.0432759}, {82.536, 0.0431411}, {82.569, 0.0430063}, {82.602, 0.0429569}, {82.634, 0.0430914}, {82.668, 0.0425955}, {82.7, 0.0425716}, {82.734, 0.0422341}, {82.767, 0.0419932}, {82.8, 0.041765}, {82.833, 0.0416967}, {82.866, 0.0416284}, {82.899, 0.0414001}, {82.933, 0.0411782}, {82.965, 0.0413094}, {82.997, 0.0414407}, {83.03, 0.041499}, {83.063, 0.041399}, {83.096, 0.0414969}, {83.13, 0.0413937}, {83.163, 0.0415185}, {83.197, 0.0414153}, {83.23, 0.0413802}, {83.262, 0.0417521}, {83.296, 0.0416805}, {83.328, 0.0420635}, {83.362, 0.0419919}, {83.395, 0.0421468}, {83.428, 0.0422415}, {83.462, 0.0420671}, {83.494, 0.0421936}, {83.527, 0.0422487}, {83.56, 0.0423039}, {83.593, 0.0425665}, {83.625, 0.0429194}, {83.659, 0.0428161}, {83.692, 0.0429425}, {83.725, 0.0430673}, {83.758, 0.0433726}, {83.791, 0.0435275}, {83.824, 0.043684}, {83.856, 0.044067}, {83.889, 0.0443834}, {83.921, 0.0448233}, {83.955, 0.04469}, {83.987, 0.045168}, {84.02, 0.045421}, {84.053, 0.0456741}, {84.086, 0.0458385}, {84.119, 0.0459301}, {84.153, 0.045792}, {84.185, 0.0461132}, {84.218, 0.0463647}, {84.251, 0.046404}, {84.284, 0.0465605}, {84.317, 0.0465555}, {84.35, 0.046712}, {84.383, 0.0468669}, {84.416, 0.0470582}, {84.449, 0.0474379}, {84.482, 0.0476577}, {84.515, 0.0478776}, {84.548, 0.0480974}, {84.581, 0.0484771}, {84.615, 0.0486287}, {84.648, 0.0488501}, {84.681, 0.0492314}, {84.715, 0.049383}, {84.748, 0.0495854}, {84.781, 0.0499335}, {84.814, 0.0502815}, {84.848, 0.0503967}, {84.881, 0.0507448}, {84.914, 0.0509123}, {84.947, 0.0512287}, {84.981, 0.0511508}, {85.013, 0.0517}, {85.046, 0.0518549}, {85.078, 0.0523851}, {85.111, 0.0526698}, {85.143, 0.0533472}, {85.176, 0.0536304}, {85.21, 0.0536807}, {85.243, 0.0539828}, {85.276, 0.0542992}, {85.309, 0.054614}, {85.341, 0.0551632}, {85.374, 0.055478}, {85.407, 0.0558292}, {85.44, 0.0562089}, {85.473, 0.0565886}, {85.507, 0.0565772}, {85.539, 0.0570282}, {85.572, 0.0574254}, {85.605, 0.0576768}, {85.638, 0.0580882}, {85.672, 0.05811}, {85.705, 0.0583615}, {85.738, 0.058632}, {85.771, 0.0590734}, {85.804, 0.059355}, {85.838, 0.0594084}, {85.87, 0.0600795}, {85.903, 0.0606587}, {85.936, 0.0611667}, {85.97, 0.0614529}, {86.002, 0.0621825}, {86.036, 0.0624687}, {86.069, 0.0629181}, {86.101, 0.0635544}, {86.134, 0.0639641}, {86.168, 0.0643105}, {86.2, 0.0649468}, {86.233, 0.0653581}, {86.266, 0.0657695}, {86.3, 0.0661159}, {86.333, 0.0665272}, {86.366, 0.0669386}, {86.398, 0.0677759}, {86.432, 0.0680289}, {86.465, 0.0685067}, {86.498, 0.068983}, {86.532, 0.0692375}, {86.565, 0.0696157}, {86.598, 0.0699289}, {86.63, 0.0706316}, {86.663, 0.0711063}, {86.696, 0.0714195}, {86.729, 0.0719354}, {86.762, 0.0723151}, {86.796, 0.0726298}, {86.829, 0.0730111}, {86.862, 0.0735523}, {86.895, 0.0740729}, {86.928, 0.0745808}, {86.961, 0.0750887}, {86.994, 0.0754368}, {87.027, 0.0759447}, {87.061, 0.0761423}, {87.093, 0.07675}, {87.126, 0.0771282}, {87.158, 0.0778974}, {87.191, 0.0784339}, {87.224, 0.0788326}, {87.257, 0.0794038}, {87.291, 0.079747}, {87.324, 0.0803183}, {87.357, 0.0808895}, {87.389, 0.0819295}, {87.422, 0.0826306}, {87.455, 0.0834915}, {87.488, 0.0841926}, {87.521, 0.0848937}, {87.554, 0.0855758}, {87.587, 0.0862436}, {87.62, 0.0870713}, {87.653, 0.0877392}, {87.686, 0.0885669}, {87.719, 0.0892347}, {87.753, 0.0896745}, {87.786, 0.0905038}, {87.819, 0.09117}, {87.852, 0.0919993}, {87.885, 0.0928255}, {87.917, 0.0935599}, {87.949, 0.0941329}, {87.983, 0.0944111}, {88.016, 0.0947576}, {88.049, 0.0950455}, {88.082, 0.0952954}, {88.115, 0.0957052}, {88.149, 0.0958853}, {88.181, 0.0963648}, {88.214, 0.0966986}, {88.247, 0.0970799}, {88.28, 0.097781}, {88.313, 0.0981607}, {88.346, 0.0988618}, {88.379, 0.0995423}, {88.412, 0.100368}, {88.444, 0.101423}, {88.477, 0.102089}, {88.51, 0.102915}, {88.543, 0.103844}, {88.576, 0.104415}, {88.609, 0.105308}, {88.642, 0.106359}, {88.674, 0.108281}, {88.708, 0.109545}, {88.741, 0.111013}, {88.774, 0.11232}, {88.807, 0.113467}, {88.84, 0.115096}, {88.873, 0.116025}, {88.905, 0.117152}, {88.938, 0.118685}, {88.971, 0.120217}, {89.004, 0.121268}, {89.036, 0.122485}, {89.069, 0.124049}, {89.102, 0.125133}, {89.136, 0.125978}, {89.169, 0.127382}, {89.202, 0.129104}, {89.234, 0.131062}, {89.267, 0.132783}, {89.3, 0.134823}, {89.333, 0.136063}, {89.367, 0.137123}, {89.4, 0.13862}, {89.433, 0.140276}, {89.466, 0.142734}, {89.499, 0.14407}, {89.532, 0.145794}, {89.565, 0.148355}, {89.598, 0.150275}, {89.631, 0.152037}, {89.665, 0.153565}, {89.697, 0.155611}, {89.731, 0.157232}, {89.763, 0.159315}, {89.796, 0.161167}, {89.829, 0.163179}, {89.862, 0.165369}, {89.896, 0.168621}, {89.929, 0.170983}, {89.962, 0.173187}, {89.994, 0.175938}, {90.027, 0.178621}, {90.06, 0.181144}, {90.093, 0.183669}, {90.127, 0.186124}, {90.16, 0.189289}, {90.194, 0.192127}, {90.227, 0.197628}, {90.259, 0.201274}, {90.292, 0.205174}, {90.325, 0.209235}, {90.358, 0.212996}, {90.392, 0.217023}, {90.425, 0.224796}, {90.457, 0.230713}, {90.491, 0.239061}, {90.523, 0.246099}, {90.556, 0.255632}, {90.59, 0.262701}, {90.622, 0.274059}, {90.655, 0.282792}, {90.688, 0.292805}, {90.721, 0.305059}, {90.753, 0.317377}, {90.786, 0.330112}, {90.819, 0.341404}, {90.852, 0.352818}, {90.885, 0.365167}, {90.918, 0.378155}, {90.951, 0.391464}, {90.983, 0.40884}, {91.016, 0.422687}, {91.048, 0.438718}, {91.081, 0.458206}, {91.115, 0.481631}, {91.148, 0.505117}, {91.182, 0.530002}, {91.214, 0.564786}, {91.247, 0.608147}, {91.28, 0.663512}, {91.313, 0.7368}, {91.347, 0.834546}, {91.381, 0.963205}, {91.414, 1.12633}, {91.446, 1.3012}, {91.479, 1.4384}, {91.511, 1.48419}, {91.545, 1.43025}, {91.578, 1.30693}, {91.61, 1.15087}, {91.643, 0.987705}, {91.675, 0.835225}, {91.708, 0.700161}, {91.742, 0.580875}, {91.775, 0.475575}, {91.808, 0.388037}, {91.842, 0.316299}, {91.874, 0.25654}, {91.908, 0.205297}, {91.941, 0.168518}, {91.974, 0.141022}, {92.006, 0.12249}, {92.04, 0.108595}, {92.072, 0.0868284}, {92.106, 0.078694}, {92.139, 0.0727048}, {92.172, 0.0618365}, {92.206, 0.0584736}, {92.238, 0.0531542}, {92.27, 0.0505546}, {92.303, 0.0475734}, {92.336, 0.0452127}, {92.369, 0.0439602}, {92.402, 0.0427077}, {92.435, 0.0411339}, {92.469, 0.0398195}, {92.501, 0.0392685}, {92.534, 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0.0166861}, {94.151, 0.0164263}, {94.185, 0.0157784}, {94.218, 0.0156784}, {94.251, 0.0154186}, {94.283, 0.0153836}, {94.317, 0.0148972}, {94.349, 0.0148639}, {94.382, 0.0146024}, {94.416, 0.014116}, {94.449, 0.0138562}, {94.483, 0.0132289}, {94.516, 0.0130007}, {94.549, 0.0127725}, {94.582, 0.0123844}, {94.615, 0.0121562}, {94.647, 0.0119566}, {94.68, 0.011665}, {94.713, 0.0113735}, {94.746, 0.0110835}, {94.779, 0.0106321}, {94.812, 0.010358}, {94.844, 0.0103214}, {94.877, 0.01006}, {94.909, 0.00986512}, {94.942, 0.00960366}, {94.977, 0.00887182}, {95.009, 0.00880519}, {95.042, 0.00851049}, {95.076, 0.0079893}, {95.108, 0.00792267}, {95.141, 0.00762955}, {95.174, 0.00749791}, {95.207, 0.00720479}, {95.24, 0.00707315}, {95.274, 0.00671343}, {95.308, 0.00633472}, {95.34, 0.00639791}, {95.373, 0.00623302}, {95.406, 0.00606972}, {95.439, 0.00574494}, {95.472, 0.00558005}, {95.505, 0.00541675}, {95.539, 0.00502379}, {95.571, 0.00524687}, {95.604, 0.00508357}, {95.637, 0.00491868}, {95.67, 0.00491369}, {95.703, 0.00475039}, {95.736, 0.0047454}, {95.769, 0.00474199}, {95.803, 0.00444718}, {95.836, 0.0043472}, {95.869, 0.00424722}, {95.902, 0.00398735}, {95.935, 0.00388579}, {95.969, 0.00348017}, {96.002, 0.00334853}, {96.036, 0.00298881}, {96.069, 0.00285559}, {96.101, 0.00295044}, {96.133, 0.00304528}, {96.166, 0.00291364}, {96.199, 0.00278042}, {96.232, 0.00280867}, {96.265, 0.00267703}, {96.298, 0.00264196}, {96.331, 0.00257206}, {96.364, 0.00250058}, {96.396, 0.00266033}, {96.43, 0.00236078}, {96.462, 0.0025617}, {96.495, 0.00255829}, {96.528, 0.0025533}, {96.561, 0.00238999}, {96.595, 0.00199704}, {96.627, 0.0022407}, {96.66, 0.00210589}, {96.693, 0.00197266}, {96.726, 0.00183944}, {96.759, 0.00186611}, {96.792, 0.00171072}, {96.824, 0.00177549}, {96.857, 0.00161061}, {96.89, 0.00160561}, {96.923, 0.00144231}, {96.956, 0.00127742}, {96.989, 0.00111412}, {97.023, 0.000881057}, {97.056, 0.000716171}, {97.089, 0.000712762}, {97.122, 0.000482968}, {97.154, 0.000611061}, {97.187, 0.000507916}, {97.22, 0.000406355}, {97.253, 0.00030321}, {97.286, 0.000342545}, {97.32, -0.0000187506}, {97.352, 0.000242324}, {97.385, 0.000112266}, {97.418, 0.000142103}, {97.451, 0.0000104619}, {97.484, -0.000121179}, {97.517, -0.00025282}, {97.55, -0.000226149}, {97.583, -0.00035779}, {97.615, -0.000297771}, {97.648, -0.00049432}, {97.681, -0.000689285}, {97.713, -0.000493118}, {97.746, -0.000528189}, {97.779, -0.000583841}, {97.812, -0.000652157}, {97.845, -0.000720474}, {97.878, -0.00078879}, {97.911, -0.000857106}, {97.944, -0.000889011}, {97.978, -0.00112524}, {98.011, -0.00113023}, {98.044, -0.00113364}, {98.077, -0.00113863}, {98.11, -0.00112304}, {98.144, -0.00132761}, {98.176, -0.00106812}, {98.209, -0.00119976}, {98.241, -0.00094027}, {98.275, -0.00114484}, {98.308, -0.00111817}, {98.341, -0.00108991}, {98.374, -0.00122155}, {98.407, -0.00119488}, {98.44, -0.00130753}, {98.473, -0.00124761}, {98.506, -0.0011877}, {98.539, -0.00128767}, {98.572, -0.00122934}, {98.604, -0.00106167}, {98.638, -0.0013264}, {98.671, -0.00136305}, {98.704, -0.0013997}, {98.737, -0.00143478}, {98.77, -0.00141444}, {98.803, -0.001516}, {98.836, -0.00145767}, {98.869, -0.00155923}, {98.902, -0.00166079}, {98.935, -0.00162304}, {98.967, -0.00152819}, {99., -0.001663}, {99.033, -0.00179622}, {99.066, -0.00176955}, {99.099, -0.00184103}, {99.132, -0.0018761}, {99.165, -0.00207265}}

which looks like this when plotted:

I am trying to estimate the areas of both peaks using at least 3 "reasonable" different baselines. Thanks to the suggestion of @JimB here: Fitting two peaks at the same time with NonLinearFit, I am estimating the areas as:

left = Select[data, #[[1]] < 82 &];
baselineleft = Mean[Select[data, #[[1]] < 70 &][[All, 2]]];
widthleft = Max[left[[All, 1]]] - Min[left[[All, 1]]];
arealeft = (Mean[left[[All, 2]]] - baselineleft)*widthleft

dright = Select[data, #[[1]] < 98 &];
right = Select[dright, #[[1]] > 84 &];
baselineright = Mean[Select[right, #[[1]] < 85 &][[All, 2]]];
widthright = Max[right[[All, 1]]] - Min[right[[All, 1]]];
arearight = (Mean[right[[All, 2]]] - baselineright)*widthright

My question is:

1) How can I estimate the area of both peaks using this methodology but using at least 3 "reasonable" baselines as to compare what would be the area of both peaks using different base lines and have and idea about the error of estimating these areas?. One example is given below with excel using two baselines where it is obvious that depending on the baseline the area of both peaks will be different. 2) How can I get this comparison of the areas of the two peaks in a table for each baseline?

Answer 1

Here is a function you can apply to your dataset, specifying the areas you want integrated. The function will:

• select the relevant portion of your dataset
• take the first and last points in that region to establish a linear baseline by linear interpolation
• describe the data in between the specified boundaries by interpolation (no point in fitting, the shape of the peak appears irrelevant to whatever the application at hand is)
• calculate the area of the peak down to the baseline, by integrating the difference of the peak and baseline interpolating functions;
• plot the result and report the area.

Here is the function's code:

ClearAll[peakArea]
peakArea[dataset_, {start_, end_}] :=
 Module[{region, peak, baseline, area},
   (*select region within data identified as the peak*)
   region = Select[dataset, start <= #[[1]] <= end &];

   (*generate interpolating functions describing the peak and baseline *)
   peak = Interpolation[region];
   baseline = Interpolation[region[[{1, -1}]], InterpolationOrder -> 1];

   (*calculate the area, subtracting the baseline*)
   area = NIntegrate[peak[x] - baseline[x], Flatten@{x, region[[{1, -1}, 1]]}];

   (*generate the plot*)
   Show[
     ListLinePlot[
       Style[dataset, Gray],
       PlotRange -> All,
       PlotLabel -> Style["Peak area: " ~~ ToString[area], Black]
     ],
     Plot[
       {
        Style[peak[x], Directive[Thick, Red]],
        Style[baseline[x], Black]
       },
       Evaluate@Flatten@{x, region[[{1, -1}, 1]]},
       PlotRange -> All,
       Filling -> {1 -> {2}}, FillingStyle -> Opacity[0.2, Red]
     ]
   ]
 ]

Using your dataset from the OP (data), here are two usage examples:

peakArea[data, {82, 95}]

peakArea[data, {62, 82}]

Answer 2

I think I found one way to do it but the areas do not seem to be correct. Here's an example with one baseline for each curve:

left = Select[data, #[[1]] < 82 &];
baselineleft = 0.056;
ipleft = Interpolation[left];


dright = Select[data, #[[1]] < 98 &];
right = Select[dright, #[[1]] > 84 &];
baselineright = 0.026;
ipright = Interpolation[right];




p1 = ListPlot[data, PlotStyle -> {{Yellow, PointSize[0.01]}}, 
   PlotRange -> {{66, 100}, All}, PlotMarkers -> {Automatic, 5}, 
   PlotLegends -> {"Original data"}, LabelStyle -> {Black, Bold, 14}];
p2 = ListLinePlot[{{65, baselineleft}, {81, baselineleft}}, 
   PlotStyle -> Black, PlotLegends -> {"Baseline 1"}];
p3 = ListLinePlot[{{82, baselineright}, {98, baselineright}}, 
   PlotStyle -> Blue, PlotLegends -> {"Baseline 2"}];
p4 = Plot[ipleft[x], {x, 67, 80}, PlotStyle -> {{Thin, Red}}, 
   PlotRange -> All, PlotLegends -> {"Fitted data"}];
p5 = Plot[ipright[x], {x, 85, 95}, PlotStyle -> {{Thin, Red}}, 
   PlotRange -> All];

Show[p1, p2, p3, p4, p5]

arealeft = NIntegrate[ipleft[x], {x, 67, 80}] - baselineleft
arearight = NIntegrate[ipright[x], {x, 85, 95}] - baselineright

which gives:

and arealeft=1.59149 and arearight=1.487459, which at least arealeft is obvously a wrong value because it cannot be bigger than arearight.

Can someone tell me what I am doing wrong here for arealeft? This area should be around 0.7-0.8.