MATLAB: How to extract X value given Y value from graph.

graphinterpolationline

I have a graph which I ploted from X and Y values. X and Y are the data vectors. Now I wnted to find values of X corresponding to perticular value of y. 
X=[0.00163629165319779	0.00919798132258265	0.0108887716090971	0.0146711509895121	0.0170727875027912	0.0183195248019579	0.0214701529053916	0.0429751397974718	0.0492808450276714	0.0535887468601313	0.0546312668441853	0.108838368209090	0.123117548287373	0.126309277779226	0.133652225605413	0.138726746967278	0.176380030642817	0.178656767960438	0.181244974266293	0.182028488504125	0.188366079912920	0.204276265010833	0.205419462095058	0.206611392842045	0.219575407312163	0.230076938132872	0.231822979086683	0.232631056161634	0.237634467232773	0.242104610234617	0.267542565734243	0.281557956744304	0.312833057094883	0.319124464220357	0.343375832711649	0.348289420385577	0.352569636089163	0.357642593625700	0.360188336139401	0.374263685881673	0.390056224874232	0.391650522675869	0.392413301822307	0.392906376647038	0.398112256101353	0.404497829354034	0.408989317941850	0.413270285981264	0.440717991244140	0.442788702297138	0.466238670974959	0.478229661633876	0.506778136096007	0.516813401433934	0.539005985379619	0.554907031467319	0.555940863634276	0.594998712090185	0.624358289172818	0.636691646673399	0.636691646673399	0.636691646673399	0.636691646673399	0.636691646673399	0.673595576899095	0.690991870967221	0.691623728204757	0.694482327270088	0.703223226864390	0.713125941582075	0.729095502236721	0.749453251696249	0.785248184904319	0.790012531082956	0.815065416646928	0.821315922015482	0.826164341954818	0.829691396788946	0.841734834718935	0.854822741928195	0.858109043192997	0.891859889006936	0.906733683367389	0.952764915345216	0.952764915345216	0.952764915345216	0.980470366913377	0.995725305844472	1.02965375760247	1.09116894860735	1.10670509719372	1.11422792999389	1.12127930245400	1.12127930245400	1.12334033118983	1.14277471093836	1.16917633244481	1.19089850966396	1.33264717043745	1.34901320716680	1.36779787738210	1.44087981077227	1.64523008957909	1.64791868775681	2.27643402946012	2.40045676947028	2.45142678398700]
Y=[0.327970660780512	0.332011235759306	0.332921494603458	0.334966833639170	0.336272047142938	0.336951613545687	0.338675071601992	0.350676523995197	0.354275568517746	0.356755561062934	0.357358328092331	0.390144287739127	0.399270422133906	0.401339342218769	0.406139930184248	0.409491004458485	0.435235365455767	0.436842919676984	0.438677608063090	0.439234531651005	0.443765372470964	0.455346819396008	0.456190529354724	0.457071870791561	0.466768441997315	0.474773779922694	0.476118038978851	0.476741456944862	0.480619720732729	0.484111312757906	0.504469097848463	0.516049003307847	0.542856789444626	0.548415510596634	0.570380400825788	0.574936780624634	0.578935485718932	0.583710823819502	0.586122035838970	0.599634471364500	0.615166607306969	0.616756803237560	0.617519073048832	0.618012319891502	0.623244115538772	0.629721998108256	0.634318708785900	0.638731195373301	0.667760657214304	0.670003487282225	0.695934458307588	0.709579482217070	0.743152374382388	0.755327344275103	0.782964775513683	0.803386803712655	0.804732868698833	0.857273337746951	0.899014193321375	0.917149276210161	0.917149276210161	0.917149276210161	0.917149276210161	0.917149276210161	0.973627548017118	1.00144444463865	1.00246961429251	1.00712073630011	1.02147703708904	1.03798894692457	1.06518092762530	1.10088015869719	1.16657580257029	1.17561063999175	1.22428363044642	1.23673808159782	1.24648599430674	1.25362549978489	1.27831360124910	1.30569436282117	1.31266115228447	1.38639837317600	1.42019536561643	1.53009968474307	1.53009968474307	1.53009968474307	1.60030840865775	1.64033208407164	1.73297416779503	1.91448899911085	1.96326411840361	1.98732634282930	2.01014827313001	2.01014827313001	2.01686820351132	2.08134856950608	2.17226025957346	2.25002870512480	2.83056628811592	2.90658351414197	2.99635450885091	3.37278249763301	4.69567928252034	4.71616719791340	13.0495320257110	15.9519723894339	17.3244414235913]
how to find value of X at Y=15? y=15 is not available in Y vector. kindly help me to write a code. Thanks

Best Answer

[Y,idx] = unique(Y) ; 
X = X(idx) ; 
iwant = interp1(Y,X,15)
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