Why am I getting this error, "Subscript indices must either be real positive integers or logicals."

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Porgs 2018-4-15

0
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https://ww2.mathworks.cn/matlabcentral/answers/394963-why-am-i-getting-this-error-subscript-indices-must-either-be-real-positive-integers-or-logicals

回答： Porgs 2018-4-15

% This code worked the last time I ran it but now I get an error message. Why is this?
      t = [-2: .001: 1.999];
      mt = sinc(5 .* t ./ pi);
      figure(1);
      plot(t, mt);
      xlabel('time');
      ylabel('amplitude');
      title('m(t)=sinc(5t/pi)');
      grid;
      PM = cos(50 .* pi + 20 .* mt);
      figure(2);
      plot(t, PM);
      xlabel('time');
      ylabel('amplitude');
      title('PM Signal');
      grid;
      % cumsum function is used to calculate integral
      integral_mt = cumsum(mt) .* 0.001;
      FM = cos(50 .* pi + 40 .* pi .* integral_mt);
      figure(3);
      plot(t, FM);
      xlabel('time');
      ylabel('amplitude');
      title('FM Signal');
      grid;