Loading and naming specific columns

Question

Anna 2011-8-30

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/14750-loading-and-naming-specific-columns

Hello,

I used this code to import and name data in Matlab:

for i=1951:2000
fileName=['arunoff_' num2str(i)];
dataStruct.(fileName)=importdata([fileName '.txt']);
end

This creates data structure dataStruct.arunoff_(i).data for each year (1951-2000). Next I would like to create and name another set of variables using the third column in 'data' (i.e. dataStruct.arunoff_1951.data(:,3), dataStruct.arunoff_1952.data(:,3) etc.). However, I don't know how to write a loop that does that and was wondering if someone could help me with this? My main problem is I don't know how to tell the loop to use data in each a_runoff(i) structure.

Hope this makes sense, thanks very much for the help!

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Answer 1

Walter Roberson 2011-8-30

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在 MATLAB Online 中打开

fn = fieldnames(dataStruct);
for K = 1:length(fn)
  newStruct.([fn 'd3']) = dataStruct.(fn).data(:,3);
end

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Andrei Bobrov 2011-8-30

Hi Walter!

Little typo.

for K = 1:length(fn)

newStruct.([fn{K} 'd3']) = dataStruct.(fn{K}).data(:,3);

end

Walter Roberson 2011-8-30

Good point. I mentally started with K = fn (i.e., iterate over the cells) and didn't clean up properly afterwards.

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Answer 2

Anna 2011-8-30

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https://ww2.mathworks.cn/matlabcentral/answers/14750-loading-and-naming-specific-columns#answer_20061

Thank you for your replies Walter and Andrei!

I used the code you supplied and it worked very well. I now have another problem though that I would really appreciate help with. I want to calculate the mean of all the values in each field in 'newStruct'. The values are arranged as one column in each field.

This is the code I tried using:

fn = fieldnames(newStruct); for K = 1:length(fn) Mean.(fn{K}) = mean(newStruct.(fn{K})); end

but I get this error: 'Subscript indices must either be real positive integers or logical'.

Anything you could suggest?