Reading certain columns of data bigger than a number into one array smaller into another

I have multiple .dat files, each of them has five columns. I only need the fifth columns and want to combine all numbers into two arrays : One only has numbers bigger than 0.7 and the other only has numbers smaller. Here is an example of .dat file

Here is the code I have so far. However, it seemed not work as expected. clc;

flist = dir(['./*.dat']); namelist = {}; for i = 1:length(flist) currentname = flist(i).name; namelist{end+1} = currentname; end

for i = 1:length(namelist) filename = namelist{i}; data = load(filename); High = data(data(:, 5)>0.7) Low = data(data(:, 5)<0.7) end Can anyone suggest a good way to work this out?

Answer 1

[Voss]

Here is the code you posted:

clc;
flist = dir(['./*.dat']);
namelist = {};
for i = 1:length(flist)
    currentname = flist(i).name;
    namelist{end+1} = currentname;
end
for i = 1:length(namelist)
    filename = namelist{i};
    data = load(filename);
    High = data(data(:, 5)>0.7)
    Low = data(data(:, 5)<0.7)
end

This will store values from the first column of data into the variables High and Low, because the indexing into data has no column index specified. To store values from the fifth column of data, you can do this instead:

clc;
flist = dir(['./*.dat']);
namelist = {};
for i = 1:length(flist)
    currentname = flist(i).name;
    namelist{end+1} = currentname;
end
for i = 1:length(namelist)
    filename = namelist{i};
    data = load(filename);
    High = data(data(:, 5)>0.7, 5)
    Low = data(data(:, 5)<0.7, 5)
end

Now, High and Low have values from the fifth column of data, but they are overwritten each time through the loop. In order to accumulate these values into two arrays with values from all the files, you can do what David Hill suggests in his answer:

clc;
flist = dir(['./*.dat']);
namelist = {};
for i = 1:length(flist)
    currentname = flist(i).name;
    namelist{end+1} = currentname;
end
High = [];
Low = [];
for i = 1:length(namelist)
    filename = namelist{i};
    data = load(filename);
    High = [High; data(data(:, 5)>0.7, 5)];
    Low = [Low; data(data(:, 5)<0.7, 5)];
end

[Lesad Li]

Thanks for your clear explanation @Benjamin. This is exactly what I want to do.

One more question, Didn't the code "data(:, 5) " already specify the 5th column?

Answer 2

[David Hill]

for i = 1:length(namelist)
    filename = namelist{i};
    data = readmatrix(filename);%try readmatrix
    High = [High;data(data(:, 5)>0.7)];%do you want to combine them
    Low  = [Low;data(data(:, 5)<0.7)];
end    

[Lesad Li]

Thanks for your answer. Yes, I want to combine all the data from different files into two arrays. It said High can not be identified