clear all;
    close all;
    clc;
    N=60;
    t=3;
    K=130;
    for M=0:0.1:1.4
        r=zeros(size(1:M));
        f=le(1/K,M);
        c=le(M,3*N/K);
        if f || c
        R2 = @(s) -(s-(s./ floor(N./s)).*M);
        LB = 1;
        UB = min(N, K);
        options = optimoptions('fmincon','Algorithm','interior-point'); % run interior-point algorithm
        [sopt, ropt] = fmincon(R2,1,[],[],[],[],LB,UB,[],options);
        r(M) = -ropt;
        end
    end
    plot(0:1.4,r(M),'r-','LineWidth',2);
    xlabel('Cache Capacity (M)');
    ylabel('Delivery Rate (R)');

Array indices must be positive integers or logical values.

Error in try (line 17)
    r(M) = -ropt;