Help with iterations over large file.

Hello everyone, I have a huge ascii.txt wind file with the following format.

time = 0 hour

2 3 4 5 6 7

0 9 8 7 6 5

7 6 5 4 3 2

9 8 7 6 5 4

time = 3 hour

2 3 4 5 6 7

0 9 8 7 6 5

7 6 5 4 3 2

9 8 7 6 5 4

The thing is that I need to flip the rows from each block between hours, like this

time = 0 hour

9 8 7 6 5 4

7 6 5 4 3 2

0 9 8 7 6 5

2 3 4 5 6 7

time = 3 hour

9 8 7 6 5 4

7 6 5 4 3 2

0 9 8 7 6 5

2 3 4 5 6 7

I can do this for one block by

X = readlines('xwind.txt');
Y = X(2:5);
Y = flip(Y);

But I couldn’t write the loop for the entire file (4865x1 string).

Any help would be much appreciated.

Answer 1

[Dyuman Joshi]

If the format of the data is homogenous through the file, try this -

in = readlines('ascii.txt')

in = 10×1 string array
    "time = 0 hour"
    "2 3 4 5 6 7 "
    "0 9 8 7 6 5"
    "7 6 5 4 3 2"
    "9 8 7 6 5 4"
    "time = 3 hour"
    "2 3 4 5 6 7 "
    "0 9 8 7 6 5"
    "7 6 5 4 3 2"
    "9 8 7 6 5 4"

for k=2:5:size(in,1)
    in(k:k+3,:) = flipud(in(k:k+3,:));
end

in

in = 10×1 string array
    "time = 0 hour"
    "9 8 7 6 5 4"
    "7 6 5 4 3 2"
    "0 9 8 7 6 5"
    "2 3 4 5 6 7 "
    "time = 3 hour"
    "9 8 7 6 5 4"
    "7 6 5 4 3 2"
    "0 9 8 7 6 5"
    "2 3 4 5 6 7 "

[gero pulido]

Thank you! It worked perfectly

[Dyuman Joshi]

You're welcome!

Answer 2

[Mathieu NOE]

hello

try this

I choosed to store each Y array into a cell

D=readlines('data.txt');    % read as string array
[eof] = size(D,1);          % last row number (end of file)

ixP1=find(contains(D,'time'));   % find the "time" line
ixP1=[ixP1 ; eof]; % add end of file line number

for k=1:numel(ixP1)-1   
    ind = ixP1(k)+1:ixP1(k+1)-1;
    Y = str2num(char(D(ind)));
    Y = flip(Y);
    out{k} = Y; % store Y flipped in cell array
end