# How would I write a function that finds the closest point from a list of coordinates?

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Joshua Rigby on 2 Apr 2022
Commented: Joshua Rigby on 2 Apr 2022
I have to write a function that calculates the distance between multiple points and a base site, then finds the closest point to the base site. This is the format I have to follow:
function [chosen_site, d] = select_closest_site( current_site, site_list, x, y )
where x and y are vectors containing the appropriate coordinates for each point, site_list is a vector with the IDs of the points that will be compared, and current_site is the base site that the distances will be calculated from.
Here's an example of how the code should function:
Consider the list of four sites, with locations x = [3, 1, 2, 2] and y = [5, 2, 4, 6]. Given current_site = 4 and site_list = [1, 3], the function should consider which of sites 1 and 3 is closer to site 4, then select site 1 as it is closer. The function should also report the distance to that site, 2:
I also have to call a function that calculates distance which I have already written. This is what I have for that:
function d = compute_distances( x_c, y_c, x, y )
d = sqrt((x_c - x).^2 + (y_c - y).^2);
end
This is what I have written so far to call in the distance function:
d = compute_distances(x(current_site), y(current_site), x, y);
How would I go about continuing past this? I assume I will have to use the min function but I'm struggling to figure out how to format it.
Any help is appreciated.

Riccardo Scorretti on 2 Apr 2022
Hi Joshua, you can try this:
x = [3, 1, 2, 2];
y = [5, 2, 4, 6];
current_site = 4;
site_list = [1, 3];
[chosen_site, d] = select_closest_site( current_site, site_list, x, y)
chosen_site = 1
d = 1.4142
function [chosen_site, d] = select_closest_site( current_site, site_list, x, y)
xc = x(current_site);
yc = y(current_site);
[d, ind] = min(sqrt((xc-x(site_list)).^2 + (yc-y(site_list)).^2));
chosen_site = site_list(ind);
end
##### 2 CommentsShowHide 1 older comment
Joshua Rigby on 2 Apr 2022
Thank you! This has really clarified it for me.

R2021a

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