Finding minimum value in while loop

Question

Takashi Fukushima 2019-11-9

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https://ww2.mathworks.cn/matlabcentral/answers/490073-finding-minimum-value-in-while-loop

评论： Takashi Fukushima 2019-11-9

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Hello,

I would like to find the minimum value in what is calculated in while loop.

I have written a program so far...

speed=input("Enter the speed: ");
D=input("Enter the distance: ");
angle=5;
throwing_distance = (speed^2) * sin(pi * angle / 90) / 9.81;
deviation=abs(D-(speed^2) * sin(pi * angle / 90) / 9.81)
while angle<45
   deviation=abs(D-(speed^2) * sin(pi * angle / 90) / 9.81); 
   angle=angle+1;
end

I would like to add if statement like,

if deviation is the minimum, display the angle.

I really appreciate if someone can help me solve this problem.

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Answer 1

Walter Roberson 2019-11-9

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在 MATLAB Online 中打开

bestdeviation = inf;
while deviation < bestdeviation
   bestdeviation = deviation;
   deviation = abs(D-(speed^2) * sin(pi * angle / 90) / 9.81); 
   angle=angle+1;
end

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Takashi Fukushima 2019-11-9

Thank you very much for your response.

I came up with this solution...

speed=input("Enter the speed: ");

D=input("Enter the distance: ");

min_deviation=abs(D-(speed^2) * sin(pi * 5 / 90) / 9.81);

angle=5;

while angle<45

deviation=abs(D-(speed^2) * sin(pi * angle / 90) / 9.81);

next_deviation=abs(D-(speed^2) * sin(pi * (angle+1) / 90) / 9.81);

next_deviation2=abs(D-(speed^2) * sin(pi * (angle+2) / 90) / 9.81);

angle=angle+1;

if deviation>=next_deviation & next_deviation<=next_deviation2

disp("Optimal angle: " + angle);

disp("Optimal deviation: " + next_deviation);

end

disp("Optimal angle: " + 5 + " Optimal deviation: " + min_deviation);

In this way, I can get the optimal(minimum) deviation and its angle.

However, I need the last statement when the if statement is never true.

For example, the optimal angle and deviation of high speed and short D like (V>=100 and D<=10) are always 5 degree since the D is within the distance of 5 degree. However, the problem is that if the if statement is true, the program shows both optimal and minimal values

I know this is another topic, but if you can help me solve the problem, I would really appreciate.

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