get the x-value of a point on curve

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?

[Jon]

Please post your code

[ahmed salah]

here is the curve

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plot(x,y)

Answer 1

[the cyclist]

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.)

[the cyclist]

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.

[ahmed salah]

Thank you

Answer 2

[Sky Sartorius]

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)

[ahmed salah]

Thank you this worked for me

[the cyclist]

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.