how to find a value of x from the graph if y=128

I don't know how to find a value of x if y given as 128 please help me to solve this question

[the cyclist]

Please give us more than a tweet-length description of your problem, and don't make us guess.

Do you have only an image of the graph? What format? PNG? TIFF? Can you post it?

Or do you have the data from the graph? Do you have x and y in numeric vectors? Can you share the data, or a small sample?

Help us help you.

Answer 1

[Star Strider]

If ‘y’ is monotonically increasing (and is otherwise compatible with all the requirements of the function), I would use interp1:

x128 = interp1(y, x, 128);

See the documentation for interp1 to understand what it requires.