get the x-value of a point on curve

33 次查看(过去 30 天)
I draw a curve between two vector of points, not a function, how can I get the x-value of a certain y-value of the curve?
  2 个评论
ahmed salah
ahmed salah 2020-2-20
here is the curve
x=[0,0.250000000000000,0.500000000000000,0.750000000000000,1,1.25000000000000,1.50000000000000,1.75000000000000,2,2.25000000000000,2.50000000000000,2.75000000000000,3,3.25000000000000,3.50000000000000,3.75000000000000,4,4.25000000000000,4.50000000000000,4.75000000000000,5,5.25000000000000,5.50000000000000,5.75000000000000,6,6.25000000000000,6.50000000000000,6.75000000000000,7,7.25000000000000,7.50000000000000,7.75000000000000,8,8.25000000000000,8.50000000000000,8.75000000000000,9,9.25000000000000,9.50000000000000,9.75000000000000,10,10.2500000000000,10.5000000000000,10.7500000000000,11,11.2500000000000,11.5000000000000,11.7500000000000,12,12.2500000000000,12.5000000000000,12.7500000000000,13,13.2500000000000,13.5000000000000,13.7500000000000,14,14.2500000000000,14.5000000000000,14.7500000000000,15,15.2500000000000,15.5000000000000,15.7500000000000,16,16.2500000000000,16.5000000000000,16.7500000000000,17,17.2500000000000,17.5000000000000,17.7500000000000,18,18.2500000000000,18.5000000000000,18.7500000000000,19,19.2500000000000,19.5000000000000,19.7500000000000,20,20.2500000000000,20.5000000000000,20.7500000000000,21,21.2500000000000,21.5000000000000,21.7500000000000,22,22.2500000000000,22.5000000000000,22.7500000000000,23,23.2500000000000,23.5000000000000,23.7500000000000,24,24.2500000000000,24.5000000000000,24.7500000000000,25,25.2500000000000,25.5000000000000,25.7500000000000,26,26.2500000000000,26.5000000000000,26.7500000000000,27,27.2500000000000,27.5000000000000,27.7500000000000,28,28.2500000000000,28.5000000000000,28.7500000000000,29,29.2500000000000,29.5000000000000,29.7500000000000,30,30.2500000000000,30.5000000000000,30.7500000000000,31,31.2500000000000,31.5000000000000,31.7500000000000,32,32.2500000000000,32.5000000000000,32.7500000000000,33,33.2500000000000,33.5000000000000,33.7500000000000,34,34.2500000000000,34.5000000000000,34.7500000000000,35,35.2500000000000,35.5000000000000,35.7500000000000,36,36.2500000000000,36.5000000000000,36.7500000000000,37,37.2500000000000,37.5000000000000,37.7500000000000,38,38.2500000000000,38.5000000000000,38.7500000000000,39,39.2500000000000,39.5000000000000,39.7500000000000,40,40.2500000000000,40.5000000000000,40.7500000000000,41,41.2500000000000,41.5000000000000,41.7500000000000,42,42.2500000000000,42.5000000000000,42.7500000000000,43,43.2500000000000,43.5000000000000,43.7500000000000,44,44.2500000000000,44.5000000000000,44.7500000000000,45,45.2500000000000,45.5000000000000,45.7500000000000,46,46.2500000000000,46.5000000000000,46.7500000000000,47,47.2500000000000,47.5000000000000,47.7500000000000,48,48.2500000000000,48.5000000000000,48.7500000000000,49,49.2500000000000,49.5000000000000,49.7500000000000,50,50.2500000000000,50.5000000000000,50.7500000000000,51,51.2500000000000,51.5000000000000,51.7500000000000,52,52.2500000000000,52.5000000000000,52.7500000000000,53,53.2500000000000,53.5000000000000,53.7500000000000,54,54.2500000000000,54.5000000000000,54.7500000000000,55,55.2500000000000,55.5000000000000,55.7500000000000,56,56.2500000000000,56.5000000000000,56.7500000000000,57,57.2500000000000,57.5000000000000,57.7500000000000,58,58.2500000000000,58.5000000000000,58.7500000000000,59,59.2500000000000,59.5000000000000,59.7500000000000,60,60.2500000000000,60.5000000000000,60.7500000000000,61,61.2500000000000,61.5000000000000,61.7500000000000,62,62.2500000000000,62.5000000000000,62.7500000000000,63,63.2500000000000,63.5000000000000,63.7500000000000,64,64.2500000000000,64.5000000000000,64.7500000000000,65,65.2500000000000,65.5000000000000,65.7500000000000,66,66.2500000000000,66.5000000000000,66.7500000000000,67,67.2500000000000,67.5000000000000,67.7500000000000,68,68.2500000000000,68.5000000000000,68.7500000000000,69,69.2500000000000,69.5000000000000,69.7500000000000,70,70.2500000000000,70.5000000000000,70.7500000000000,71,71.2500000000000,71.5000000000000,71.7500000000000,72,72.2500000000000,72.5000000000000,72.7500000000000,73,73.2500000000000,73.5000000000000,73.7500000000000,74,74.2500000000000,74.5000000000000,74.7500000000000,75,75.2500000000000,75.5000000000000,75.7500000000000,76,76.2500000000000,76.5000000000000,76.7500000000000,77,77.2500000000000,77.5000000000000,77.7500000000000,78,78.2500000000000,78.5000000000000,78.7500000000000,79,79.2500000000000,79.5000000000000,79.7500000000000,80];
y=[-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-1000000000.00000;-999023914.181976;-996101369.470118;-991249448.402318;-984496437.005408;-975881550.135659;-965454552.197838;-953275278.375072;-939413062.813476;-923946081.405808;-906960617.887384;-888550262.878127;-868815056.262843;-847860583.886983;-825797039.950101;-802738266.700420;-778800783.071405;-754102813.758623;-728763329.919491;-702901112.199745;-676633846.161729;-650077259.426284;-623344308.959634;-596544425.958485;-569782824.730923;-543159880.858705;-516770582.779577;-490704059.767441;-465043188.134056;-439864276.347883;-415236828.681841;-391223385.978341;-367879441.171442;-345253426.344544;-323386767.337505;-302314001.257049;-282062951.693815;-262654956.011189;-244105138.745554;-226422724.943098;-209611387.151098;-193669619.776293;-178591134.612436;-164365271.515199;-150977418.455915;-138409435.506143;-126640077.682188;-115645412.001621;-105399224.561864;-95873413.9333128;-87038367.6562235;-78863319.1321027;-71316682.6977580;-64366365.1556118;-57980052.5002544;-52125471.0225585;-46770622.3839590;-41883992.6308008;-37434735.4590011;-33392830.3407140;-29729216.3861588;-26415903.0350821;-23426058.8540209;-20734079.8588388;-18315638.8887342;-16147717.6303287;-14208622.9311963;-12477989.0542226;-10936767.5106050;-9567206.07335306;-8352818.51808101;-7278346.56690364;-6329715.42748575;-5493984.22569959;-4759292.52969696;-4114804.05804821;-3550648.55724255;-3057862.72632757;-2628330.96056771;-2254726.58323161;-1930454.13622771;-1649593.20729371;-1406844.18457416;-1197476.24923513;-1017277.84361470;-862509.786462451;-729861.148096995;-616407.946691314;-519574.682154838;-437098.685902352;-366997.232797294;-307537.335293304;-257208.118800665;-214695.661081271;-178860.166527008;-148715.338006110;-123409.804086680;-102210.457403375;-84487.5602850465;-69701.4761011665;-57390.8887394688;-47162.3778574823;-38681.2237531849;-31663.3226067570;-25868.1002226541;-21092.3200481345;-17164.6889911202;-13941.1722657260;-11300.9360431463;-9142.84398775726;-7382.44074333424;-5949.36205084747;-4785.11739212903;-3841.19684131568;-3077.45915842322;-2460.76307630544;-1963.80822089881;-1564.15617842291;-1243.40590008523;-986.500936172905;-781.148940830449;-617.336511316966;-486.924746716508;-383.312956548538;-301.159744605734;-236.152261880159;-184.815787720481;-144.356982138370;-112.535174719259;-87.5569356105099;-67.9899287062702;-52.6926920127339;-40.7575393356832;-31.4642435108093;-24.2425556547795;-18.6419473328348;-14.3072419185677;-10.9590354849177;-8.37800305312445;-6.39234879527583;-4.86779390210820;-3.69960765354966;-2.80627950629673;-2.12450593559293;-1.60522805518561;-1.21050699313975;-0.911065565816399;-0.684358602861398;-0.513061702609176;-0.383890383971262;-0.286679499687312;-0.213667176299877;-0.158939100945165;-0.117998221631021;-0.0874323075473376;-0.0646576904591947;-0.0477221722017458;-0.0351537765491551;-0.0258449407447336;-0.0189640399835250;-0.0138879438649640;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000;1000000000.00000];
plot(x,y)

请先登录,再进行评论。

采纳的回答

the cyclist
the cyclist 2020-2-20
When you say "get", do you mean from the vectors, or only from the curve?
If you mean from the data, you can do, for example
x(y==0.25)
(You might need to be careful if y is not exactly 0.25, due to floating point precision.)
  2 个评论
the cyclist
the cyclist 2020-2-20
My solution assumes the y value you are looking for is in the original vector. Sky Sartorius's solution is preferred if the y value is not in the original vector, but you want to interpolate.

请先登录,再进行评论。

更多回答(1 个)

Sky Sartorius
Sky Sartorius 2020-2-20
This is a table lookup / interpolation problem. For your data, you'll first have to make sure there aren't any repeated y values.
yQuery = -2.6e8; % Example query point.
[Y,ind] = unique(y,'stable')
X = x(ind);
x = interp1(Y,X,yQuery)
  2 个评论
the cyclist
the cyclist 2020-2-20
The best way to thank a contributor is to upvote and/or accept their answer. This rewards them with reputation points, and also directs future users to solutions.

请先登录,再进行评论。

类别

Help CenterFile Exchange 中查找有关 2-D and 3-D Plots 的更多信息

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by