This code shows an example
x = rand(2,2,2);
val = 0.5;
[~,idx] = min(abs(x-val), [], 'all', 'linear');
[i1,i2,i3] = ind2sub(size(x), idx); % return index in each dimension
closest_value = x(i1,i2,i3);
The following is equivalent to the above code but convenient to use if the number of dimensions is large.
x = rand(2,2,2);
val = 0.5;
[~,idx] = min(abs(x-val), [], 'all', 'linear');
[i{1:3}] = ind2sub(size(x), idx); % return index in each dimension
closest_value = x(i{:});
