MATLAB Answers

How to extract X value given Y value from graph.

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Govind Kumar
Govind Kumar on 8 May 2020
Commented: Govind Kumar on 8 May 2020
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

Accepted Answer

KSSV
KSSV on 8 May 2020
[Y,idx] = unique(Y) ;
X = X(idx) ;
iwant = interp1(Y,X,15)

More Answers (1)

Rik
Rik on 8 May 2020
You can treat x as y and y as x. That way you can use normal interpolation and curve fitting tools.

  3 Comments

madhan ravi
madhan ravi on 8 May 2020
+1 , Rik you beat me up by a few seconds xD
Govind Kumar
Govind Kumar on 8 May 2020
No I can't use curve fitting tool. I have to use this code on loop. Can you goe me code for interploation?
Govind Kumar
Govind Kumar on 8 May 2020
From fig I can see for Y=8 x will be approx 2. So is their any method so I can extract excact value by code

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