How to efficiently Assign Value to column vector?

Question

balandong 2017-7-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/349910-how-to-efficiently-assign-value-to-column-vector

评论： balandong 2017-7-23

Dear Coder, Any idea how to remove the two for loop to assign multiple value to a column vector? Really appreciate for the help.

The patients.mat is build-in mat file in MATLAB 2017

load patients
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
[tf,Ioc_Alert_LessThree] = find (ismember(Smoker, 1)); 
for i = 1: length (tf)
    M (i,1) = Height (tf(i));
end
[tgf,Ioc_Alert_two] = find (ismember(Smoker, 0)); 
for i = 1: length (Ioc_Alert_two)
  M (i,2) = Height (tgf(i));
end
M(M == 0) = NaN;
NonSmoker(Ioc_Alert_two == 1) = 0;
Yes_Smoker(Ioc_Alert_LessThree == 1) = 1;
scatter ( M (1:34,1),Yes_Smoker)
hold on
scatter ( M (:,2),NonSmoker)

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Image Analyst 2017-7-23

编辑：Image Analyst 2017-7-23

It would be easier for people to help you if you attached patients.mat. Then they could run your code.

balandong 2017-7-23

patients.mat is build-in mat file in MATLAB 2017

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Answer 1

Geoff Hayes 2017-7-23

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https://ww2.mathworks.cn/matlabcentral/answers/349910-how-to-efficiently-assign-value-to-column-vector#answer_275227

在 MATLAB Online 中打开

balandong - your first for loop is

 for i = 1: length (tf)
    M (i,1) = Height (tf(i));
 end

Try replacing this with

M = zeros(length(tf),1);
M(1:length(tf)) = Height(tf(1:length(tf)))

Something similar can be done for the second for loop too.

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balandong 2017-7-23

在 MATLAB Online 中打开

Thanks Geoff, Your suggestion is more compact, indeed.

The full code is as following.

load patients
[tf,Ioc_Alert_LessThree] = find (ismember(Smoker, 1)); 
[tgf,Ioc_Alert_two] = find (ismember(Smoker, 0)); 
M = zeros(length(tgf),2);
M(1:length(tf),1) = Height(tf(1:length(tf)));
M(1:length(tgf),2) = Height(tgf(1:length(tgf)));

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