I am getting the following error for the below code: Subscript indices must either be real positive integers or logicals. How can i remove that error.

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Sattik Basu 2017-8-19

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https://ww2.mathworks.cn/matlabcentral/answers/353357-i-am-getting-the-following-error-for-the-below-code-subscript-indices-must-either-be-real-positive

回答： Walter Roberson 2017-8-20

采纳的回答： Walter Roberson

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clc
clear all
g=9.81;
u=10;
t=0:.1:10;
y(1)=0;
while (y(t)>=0)
y(t)=(u*t)-(0.5*g*t.*t)
end

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Sattik Basu 2017-8-19

编辑：Walter Roberson 2017-8-20

在 MATLAB Online 中打开

i found a different solution to this:

g=9.81;
u=100;
t=0;
y=0;
while (y>=0)
      disp(['at t=', num2str(t) ', the height is=', num2str(y)])
      t=t+0.1;
      y=(u*t)-(0.5*g*t^2);
end

why does this work and not the first one?

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采纳的回答

Walter Roberson 2017-8-20

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https://ww2.mathworks.cn/matlabcentral/answers/353357-i-am-getting-the-following-error-for-the-below-code-subscript-indices-must-either-be-real-positive#answer_278574

在 MATLAB Online 中打开

You have

t=0:.1:10;

so t is a vector containing 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0

You have

while (y(t)>=0)

but t is the vector discussed above, so your line is equivalent to asking

while y([0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0]) >= 0

However, this attempts to subscript y with 0 and non-integers.

I suggest you have a look at https://www.mathworks.com/matlabcentral/answers/353353-how-can-i-use-interval-with-decimal-at-the-end-of-a-count-in-for-loop-e-g-t-1-1-18-7#comment_478299

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