I am not certain what you want. If you want lines to only go an intersection of another line, try something like this —
x = linspace(0, 60);
y = @(x) 20*x; % Equation of Blue Line
figure
plot(x, y(x), '-b', 'LineWidth',2.5)
hold on
x1 = 27;
plot([1 1]*x1, [0 y(x1)], '--g')
plot([0 x1], [1 1]*y(x1), '--r')
hold off
grid
Make appropriate changes to get the result you want for the other lines. Iv you have a vector of independent variable values, consider using a loop.
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