How do I set the value of Y axis =0.02, and the plot will show me the value of x?

Hello guys, I wanna the value of X-axis when the Y-axis is at exactly 0.02, at C=80. How can I do that. Because when I move the cursor manually on the plot, I cant get a Y-axis value exaclty =0.02.

Answer 1

[Star Strider]

Use the interp1 function —

x = logspace(-1, 2, 50);
y = -x.^3;

yi = -0.02;
xi = interp1(y, x, yi)

xi = 0.2710

figure
loglog(x, y)
hold on
plot(xi, yi, 'r+', 'MarkerSize',10)
plot([min(xlim) xi], [1 1]*yi, '--k')
plot([1 1]*xi, [min(ylim) yi], '--k')
hold off
grid

.