If Loop for specific condition

Question

Fereizqo Sulaiman 2018-2-27

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/385108-if-loop-for-specific-condition

回答： Esha Almas 2020-3-4

Hello, i've written the following script in MATLAB:

i = 1:0.5:50;
for t = [-5:0.5:50]
    if t<10
        v = 11.*t.^2 - 5.*t;
    elseif t<20.5 && t>10
        v = 1100-5.*t;
    elseif t<30.5 && t>20
        v = 50.*t + 2.*(t-20).^2;
    elseif t>30
        v = 1520.*exp(-0.2.*(t-30));
    else
        v = 0;
    end
    end
fprintf('value of v: %d\n', v);

I want to get value of v in every t condition First condition, t < 10 Second condition, 10<t<20 Third condition, 20<t<30 Forth condition, t>30 and if none of them, the value of v is 0 Thanks for your help

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Answer 1

KL 2018-2-27

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https://ww2.mathworks.cn/matlabcentral/answers/385108-if-loop-for-specific-condition#answer_307364

在 MATLAB Online 中打开

is it a homework? should you really use for loop and if-else statements?

I suppose yes. In that case, you need to store your calculated v after every iteraton. For example,

t = -5:0.5:50; %here you define t

and you may want to store v for every t, so pre-allocate v for the same size now,

v = zeros(size(t));

now, v is full of zeros. Fill it up inside your loop. It's always wise to use a indexing variable as for-loop counter,

 for indx=1:numel(t)
   if(t(indx) <= condition)
     v(indx) = some equation
   elseif ...
     ...
   end
 end

get the idea?

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Fereizqo Sulaiman 2018-3-7

No, i am trying to learn matlab by myself from a book then get stuck with this exercise. I understand, thanks for your help

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Answer 2

Andrei Bobrov 2018-2-27

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链接

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https://ww2.mathworks.cn/matlabcentral/answers/385108-if-loop-for-specific-condition#answer_307374

在 MATLAB Online 中打开

t = -5:0.5:50;  
tt = [-inf,10,20,30,inf];
f = {@(t)11*t.^2 - 5*t;
    @(t)1100-5*t;
    @(t)50*t + 2*(t-20).^2;
    @(t)1520.*exp(-.2*(t-30))};
ii = discretize(t,tt);
v = arrayfun(@(x,y)x{:}(y),f(ii),t(:));