Finding approximate y values for corresponding x values in matlab

Suppose I have a graph (formed from data) that has x and y values, but it is not analytic (so not continuous). I need to find a way such that for any x value, matlab will find the closest x value on the graph and give me the corresponding y value. Any ideas?

for example:

x y

1 2

2 5

3 8

4 13

5 23

6 49

So say that is my function, and I want to find the y value that corrisponds to x = 3.1 or 5.2, etc. The data is weird so I cant to a trivial linear approximation or something like that for the whole graph.

Answer 1

[Fangjun Jiang]

interp1(x,y,3.1,'nearest')

[Aleksandr Shmidt]

just ran the snip in the code, 'nearest' will aproximate to the closest value in the data instead of finding value by the trend

[Fangjun Jiang]

That is what the OP wanted. "find the closest x value on the graph and give me the corresponding y value".

Answer 2

[Santiago Alcantara]

A first aproach that you can use is the function "polyxpoly"( https://es.mathworks.com/help/map/ref/polyxpoly.html).

Another aproach is:

[val_1,idx_1]=min(abs(x-y))

This is usefull when the values are not exact values. You will find the minimun difference near to cero and exactly index to play with.