How to find a point on this plot?

Hello!

I'm trying to get the coordinates from a graph when Y cross the X axis (Y=0) and I'm having trouble finding this solution. The plot is basically a combination of points (X and Y) and do not necessarily have integer values. How can I proceed? Thanks

Here is an example of this plot:

X = [-205078000000000,00 -190430000000000,00 -175781000000000,00 -156250000000000,00 -141602000000000,00 -117188000000000,00 -102539000000000,00 -0.927730000000000 -0.781250000000000 -0.732420000000000 -0.537110000000000 -0.341800000000000 -0.195310000000000 0,00 0,00 0.195310000000000 0.292970000000000 0.439450000000000 0.683590000000000 0.732420000000000 0.878910000000000 0.976560000000000 112305000000000,00 136719000000000,00 151367000000000,00 170898000000000,00 190430000000000,00 205078000000000,00 224609000000000,00 229492000000000,00 253906000000000,00 268555000000000,00 283203000000000,00 302734000000000,00 317383000000000,00 332031000000000,00 332031000000000,00 341797000000000,00 351563000000000,00 351563000000000,00 361328000000000,00 375977000000000,00 395508000000000,00 410156000000000,00 415039000000000,00 434570000000000,00 449219000000000,00 454102000000000,00 463867000000000,00 463867000000000,00 473633000000000,00 473633000000000,00 478516000000000,00 493164000000000,00 493164000000000,00 517578000000000,00 527344000000000,00 541992000000000,00 556641000000000,00 556641000000000,00 571289000000000,00 585938000000000,00 610352000000000,00 625000000000000,00 649414000000000,00 668945000000000,00 673828000000000,00 683594000000000,00 693359000000000,00 703125000000000,00 717773000000000,00 722656000000000,00 732422000000000,00 742188000000000,00 742188000000000,00 756836000000000,00 761719000000000,00 766602000000000,00 776367000000000,00 771484000000000,00 786133000000000,00 786133000000000,00 800781000000000,00 815430000000000,00 820313000000000,00 834961000000000,00 839844000000000,00 864258000000000,00 878906000000000,00 888672000000000,00 898438000000000,00 903320000000000,00 908203000000000,00 917969000000000,00 922852000000000,00 932617000000000,00 957031000000000,00 986328000000000,00 102050800000000,00 104980500000000,00 106933600000000,00];

Y = [-599739554,78 -592692899,06 -585506566,66 -578279633,17 -570989523,41 -563491989,06 -556244088,36 -549103770,37 -542052956,48 -535074784,20 -527790864,49 -520300201,53 -512578856,84 -505085873,20 -497922253,87 -490469464,07 -482829624,94 -475103570,06 -467389867,06 -459544952,05 -451309009,84 -442905023,74 -434313642,96 -425753113,26 -417197361,63 -408380357,33 -399517893,17 -390464118,51 -381435719,92 -372531106,70 -363367781,94 -353921258,30 -343925703,27 -333718484,48 -323635657,72 -313532373,15 -303509237,80 -293189267,41 -282435147,05 -271229641,22 -259677782,79 -248242552,53 -236778917,55 -225139611,40 -213059945,34 -200518042,22 -187970390,89 -175271962,77 -162281991,85 -148741072,85 -134631399,94 -120296203,82 -105476980,93 -90153609,80 -74182708,22 -57539659,82 -40556371,36 -22961799,25 -4846997,45 13695312,86 32690081,45 52045480,45 72037101,38 92461238,40 113355702,71 134880430,21 156831072,44 179358633,58 202372519,02 226024807,22 250348801,76 275016871,16 300302132,57 326116714,50 352492722,64 379582271,39 407178786,87 435436666,75 464268793,30 493949086,28 524630692,18 556108378,52 588660907,86 622089281,37 656437508,95 691868860,42 728427166,74 766400618,17 805360016,95 845237609,53 886203228,12 928184532,61 971469553,39 1015865477,26 1061422731,82 1108313448,57 1156353913,06 1205731942,44 1256402226,25 1308563976,55 1362294061,31];

Answer 1

[John D'Errico]

X = [-205078000000000.00  -190430000000000.00  -175781000000000.00  -156250000000000.00  -141602000000000.00  -117188000000000.00  -102539000000000.00  -0.927730000000000  -0.781250000000000  -0.732420000000000  -0.537110000000000  -0.341800000000000  -0.195310000000000  0.00  0.00  0.195310000000000  0.292970000000000  0.439450000000000  0.683590000000000  0.732420000000000  0.878910000000000  0.976560000000000  112305000000000.00  136719000000000.00  151367000000000.00  170898000000000.00  190430000000000.00  205078000000000.00  224609000000000.00  229492000000000.00  253906000000000.00  268555000000000.00  283203000000000.00  302734000000000.00  317383000000000.00  332031000000000.00  332031000000000.00  341797000000000.00  351563000000000.00  351563000000000.00  361328000000000.00  375977000000000.00  395508000000000.00  410156000000000.00  415039000000000.00  434570000000000.00  449219000000000.00  454102000000000.00  463867000000000.00  463867000000000.00  473633000000000.00  473633000000000.00  478516000000000.00  493164000000000.00  493164000000000.00  517578000000000.00  527344000000000.00  541992000000000.00  556641000000000.00  556641000000000.00  571289000000000.00  585938000000000.00  610352000000000.00  625000000000000.00  649414000000000.00  668945000000000.00  673828000000000.00  683594000000000.00  693359000000000.00  703125000000000.00  717773000000000.00  722656000000000.00  732422000000000.00  742188000000000.00  742188000000000.00  756836000000000.00  761719000000000.00  766602000000000.00  776367000000000.00  771484000000000.00  786133000000000.00  786133000000000.00  800781000000000.00  815430000000000.00  820313000000000.00  834961000000000.00  839844000000000.00  864258000000000.00  878906000000000.00  888672000000000.00  898438000000000.00  903320000000000.00  908203000000000.00  917969000000000.00  922852000000000.00  932617000000000.00  957031000000000.00  986328000000000.00  102050800000000.00  104980500000000.00  106933600000000.00];
Y = [-599739554.78  -592692899.06  -585506566.66  -578279633.17  -570989523.41  -563491989.06  -556244088.36  -549103770.37  -542052956.48  -535074784.20  -527790864.49  -520300201.53  -512578856.84  -505085873.20  -497922253.87  -490469464.07  -482829624.94  -475103570.06  -467389867.06  -459544952.05  -451309009.84  -442905023.74  -434313642.96  -425753113.26  -417197361.63  -408380357.33  -399517893.17  -390464118.51  -381435719.92  -372531106.70  -363367781.94  -353921258.30  -343925703.27  -333718484.48  -323635657.72  -313532373.15  -303509237.80  -293189267.41  -282435147.05  -271229641.22  -259677782.79  -248242552.53  -236778917.55  -225139611.40  -213059945.34  -200518042.22  -187970390.89  -175271962.77  -162281991.85  -148741072.85  -134631399.94  -120296203.82  -105476980.93  -90153609.80  -74182708.22  -57539659.82  -40556371.36  -22961799.25  -4846997.45  13695312.86  32690081.45  52045480.45  72037101.38  92461238.40  113355702.71  134880430.21  156831072.44  179358633.58  202372519.02  226024807.22  250348801.76  275016871.16  300302132.57  326116714.50  352492722.64  379582271.39  407178786.87  435436666.75  464268793.30  493949086.28  524630692.18  556108378.52  588660907.86  622089281.37  656437508.95  691868860.42  728427166.74  766400618.17  805360016.95  845237609.53  886203228.12  928184532.61  971469553.39  1015865477.26  1061422731.82  1108313448.57  1156353913.06  1205731942.44  1256402226.25  1308563976.55  1362294061.31];

Using the code from Doug Schwarz's intersections code from the FEX, it is as easy as thiis:

format long g
xloc = intersections(X,Y,[min(X),max(X)],[0 0])

xloc = 
           556641000000000

Find intersections on the FEX, here:

https://www.mathworks.com/matlabcentral/fileexchange/11837-fast-and-robust-curve-intersections?s_tid=srchtitle

[Rodrigo Cicareli]

Works like a charm! Thank you!