code loop occur errors

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John fredson 2022-5-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1723715-code-loop-occur-errors

评论： dpb 2022-5-20

m = 0.5;
g = 9.81;
F = m*g;
theta = 0:50
V = sqrt(2*F/m);
vertical = V*sin(theta);
pve = V_hi > 0;
t_pve = theta(pve);
for i = 1:length(V_vi)
    for j = 1:length(t_pve)
        j = j+1;
        while vertical(i) > 4.65
            vertical(i) = Vertical_new;
        end
    end
end

I wanna obtain all the Vertical_new which satisfied the while loop condition, why it won't run? This is the error shown

Unrecognized function or variable 'Vertical_new'

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John fredson 2022-5-20

编辑：John fredson 2022-5-20

yup, means that vertical > 4.65 will be put into Vertical_new

dpb 2022-5-20

在 MATLAB Online 中打开

...
for i = 1:length(V_vi)
  for j = 1:length(t_pve)
    j = j+1;
    while vertical(i) > 4.65
      vertical(i) = Vertical_new;
    end
  end
end

Besides the other comments, there's nothing inside the loop over j that is dependent upon what j is; it simply repeats the same assignment of i element of array length(t_pve) times.

Secondly, you try to change the loop indexing variable j each time inside the loop -- this is not kosher; see the documentation for for that has an explanation/note about it. Even if it were used, the loop construct would reset it to the loop counter value each pass through the loop, anyway...

Thirdly, you referenced a variable V_hi that looks to have been intended to be the height against to test; but as others noted, it's not defined. Assign it the value of the constant and don't bury "magic" numbers of that sort in the code; use variables that can be changed easily/documented.

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