Accessing elements in a structure

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C.G. 2021-7-27

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/886824-accessing-elements-in-a-structure

编辑： Stephen23 2021-7-27

采纳的回答： KSSV

out.mat

I have 2 matlab files, both containing 2 elements: velocity and points.

i have loaded these two files into a structure, but now I want to access each individual field in the velocity column and do some calculations in it (e.g. work out the mean value).

I am struggling to access each field, could anybody help me please?

file = dir('*.mat'); 
num_files = length(file); 
[~, index] = natsort({file.name}); 
filelist = file(index);
out = load(filelist(1).name);
for k = 1:numel(filelist)
    out(k) = load(filelist(k).name); 
end

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Stephen23 2021-7-27

编辑：Stephen23 2021-7-27

Unless you have a good reason for using NATSORT you should probably use NATSORTFILES:

https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort

which lets you write simpler code by directly sorting the output from DIR:

P = 'absolute or relative filepath to where the files are saved';
S = dir(fullfile(P,'*.mat'));
S = natsortfiles(S); % <------- much simpler!
for k = 1:numel(S)
    F = fullfile(P,S(k).name)
    ... etc
end

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采纳的回答

KSSV 2021-7-27

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/886824-accessing-elements-in-a-structure#answer_754634

编辑：KSSV 2021-7-27

file = dir('*.mat'); %fine all the .mat files
num_files = length(file); %record how many files have been found
[~, index] = natsort({file.name}); %sort the files into order
filelist = file(index);
GTav = zeros(numel(filelist),1)
for k = 1:numel(filelist)
    load(filelist(k).name); % I hope the structure is named out in every file           
    % For each cell in the velocity column of the structure
    v1 = vel ;
    %1. calculate the resultant velocity of each particle
    ResV = sqrt((v1(:,1).^2) + (v1(:,2).^2) + (v1(:,3).^2));
    %2. calculte the mean resultant velocity of all the particles
    ResVav = mean(ResV);
    %3. calculate the granular temperature of all the particles
    GT = ResV-ResVav;
    %4. calculate the average granular temperature for each field
    GTav(k) = mean(GT);
end