reading data from plots

I want to determine the time duration between the first and the last instant when the y value for the (t,y) plot becomes 1% of the maximum y vale; (t may have mutiple values when y becomes 1% of max);I can find max value of y with indexmax = find(max(y) == y); ymax = y(indexmax); need help with the code; thanks

Answer 1

[KSSV]

use

idx= find(y==ymax*1/100); % 1 % of maximum value

doc find