Try this:
x = [-1.9 2; -1.8, 1.8; -1.5, 1.3]
y = [0, 0.05, 0.1]
plot(x(:,1), y, 'b*-', 'LineWidth', 2);
hold on;
grid on;
plot(x(:, 2), y, 'rd-', 'LineWidth', 2);

Look how each Y value occurs at two different X values.
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