Reading data from CSV file takes too long any suggestion ?

Question

mohsen moslemin 2016-9-5

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/301935-reading-data-from-csv-file-takes-too-long-any-suggestion

评论： mohsen moslemin 2016-9-5

clc
clear
tic
format long
files= dir('E:\PIV\*.csv');
num_files = length(files);
   data_length = cell(1,num_files);
   for(i=1:1:num_files);
   %import all data from Column E to K
   data_length{i} = xlsread(files(i).name,'E:K');
    A = cell2mat(data_length);
    i = 3:7:(num_files-1)*7+3;
    j = 4:7:(num_files-1)*7+4;
    k = sort([i j]);
    %Remove two columns G and H 
    A(:,k)=[];
    % defining mask area
    r = 55/2;
    p = r+2;
    i = 1:5:(num_files-1)*5+1;
    j = 2:5:(num_files-1)*5+2;
    x = A(:,i);
    y = A(:,j);
    R = (x-p).^2+(y-p).^2<=r^2;
    k = 5:5:(num_files-1)*5+5;
    Le = A(:,k).*R;
    Le(Le==0) = [];
    x=A(:,i).*R;
    x(x==0) = [];
    y=A(:,j).*R;
    y(y==0) = [];
    standard_deviation_Le=std(Le);
    k = 4:5:(num_files-1)*5+4;
    velocity_v=A(:,k).*R;
    velocity_v(velocity_v==0) = [];
    positive_velocity_v=abs(velocity_v);
    standard_deviation_v=std(positive_velocity_v);
    k = 3:5:(num_files-1)*5+3;
    velocity_u=A(:,k).*R;
    velocity_u(velocity_u==0) = [];
    positive_velocity_u=abs(velocity_u);
    standard_deviation_u=std(positive_velocity_u);
    TKE=0.5*(standard_deviation_u^2+standard_deviation_v^2+((standard_deviation_u+standard_deviation_v)/2)^2);
    number=numel(x)/num_files;
    %Averaging Velocity u
    E=reshape(velocity_u,number,num_files);
    E=E';
    E=var(E);
    %Averaging Velocity v
    W=reshape(velocity_v,number,num_files);
    W=W';
    W=var(W);
    %Averaging x
    X=reshape(x,number,num_files);
    X=X';
    X=mean(X);
    %Averaging y
    Y=reshape(y,number,num_files);
    Y=Y';
    Y=mean(Y);
    scale_factor = 0.1;
    figure
    quiver(X,Y,E*scale_factor,W*scale_factor,'AutoScale','off')
    end