how to store the conditional loop data

Question

Chaudhary P Patel 2022-4-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1708095-how-to-store-the-conditional-loop-data

评论： Jan 2022-4-29

sir/ madam please correct me.

ut=rand(15,1);
uy=([0.84;0.384;0.784]);
eval (['U_y','=[u_y;u_y;u_y;u_y;u_y]']);
for n=1:15
    if ut(n,1)<=U_y(n,1)
        ut(n,1)=ut(n,1);
    else
        ut(n,1)=0;
    end
    utt(:,1)=ut(n,1);    %% i want to store the ut as a utt in a column
end

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Star Strider 2022-4-29

My code tests each element of ‘ut’ against ‘U_y’ and sets it to zero if the condition is satisfied.

What result do you want?

Jan 2022-4-29

在 MATLAB Online 中打开

@Chaudhary P Patel: The line ut(n,1)=ut(n,1) replaced the n.th element of the vector ut by the n.th element of the vector ut. This is a waste of time only.

An option to avoid this (see others in the already provided answers):

for n = 1:15
    if ut(n) <= U_y(n)
        utt(n) = ut(n);
    else
        utt(n) = 0;
    end
end

Or with a proper pre-allocation, to avoid the time-consuming growing of arrays:

utt = zero(15, 1);  % The default value is 0 now
for n = 1:15
    if ut(n) <= U_y(n)
        utt(n) = ut(n);
    end
end

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Answer 1

Star Strider 2022-4-29

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1708095-how-to-store-the-conditional-loop-data#answer_953660

在 MATLAB Online 中打开

If I understand the code correctly, it can be simply stated as:

ut=rand(15,1);
u_y=([0.84;0.384;0.784]);
U_y = [u_y;u_y;u_y;u_y;u_y];                            % Create Column Vector
utt = ut;                                               % Copy 'ut' to 'utt'
utt(ut>U_y) = 0                                         % Set Appropriate Elements To Zero
utt = 15×1
         0
         0
    0.6317
    0.7311
    0.1069
    0.5889
    0.5515
         0
    0.2595
    0.3677

No loops!

.

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Answer 2

Jan 2022-4-29

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1708095-how-to-store-the-conditional-loop-data#answer_953670

在 MATLAB Online 中打开

Your cleaned code:

ut  = rand(15, 1);
uy  = [0.84; 0.384; 0.784];
U_y = repmat(uy, 5, 1);
for n = 1:15
    if ut(n) > U_y(n)
        ut(n) = 0;
    end
    utt(n) = ut(n);
    %   ^ insert an index here
end