How does this work? (I'm assuming T.y is monotonically increasing)
% example table:
x = randi(10,59,1);
y = cumsum(rand(59,1));
z = randi([10 20],59,1);
R = randi([2 3],59,1);
T = table(x, y, z, R);
% example user input:
yin = range(T.y)*rand + min(T.y);
%---------------------------------
% location of row of interest:
idx = find(yin > T.y, 1, 'last');
% row of interest:
vars = T{idx,:};
% vars is a 1x4 array containing the x, y, z, and R to use in your equation
