Downloading data from txt file

I was trying to download data from txt file using the importdata function however it downloads it into a structure with cell arrays in it. this is the code I am using. I need this data in a matrix of doubles if possible but it won't work.

delimiterIn = ' ';
[DataStructure] = importdata('iss.txt',delimiterIn);

DataCells = DataStructure(1).textdata(:,:);

This is a sample of what the txt file has inside:

1 25544U 98067A   16001.21631944  .00005382  00000-0  85171-4 0  9992
2 25544  51.6436 175.7680 0008248 349.1433 350.2600 15.55191287978846
1 25544U 98067A   16001.28471065  .00005383  00000-0  85187-4 0  9993
2 25544  51.6436 175.4264 0008246 349.3894  13.1693 15.55192096978860
1 25544U 98067A   16001.49479696  .00005567  00000-0  87829-4 0  9993
2 25544  51.6434 174.3772 0008262 350.0277 109.5268 15.55195766978890
1 25544U 98067A   16001.49479696  .00005567  00000-0  87829-4 0  9993
2 25544  51.6434 174.3772 0008262 350.0277 109.5268 15.55195766978890
.
.
.

[Cedric]

Which data do you need? What about the ones with letters/dashes? Do you want to discard them, to extract them in a separate array, ..? They have 9 columns actually, whereas the others have 8.

[Jesus Christian]

I need the entire bottom row of every set in one array of 8 elements (i.e. the rows with a 2 as first element)

I also need the top row (rows with 1 as a first element) but only the elements without letters

Basically, I need all the elements on each row that don't have letters.

Answer 1

[Cedric]

Here is one way:

 data = textscan( fileread( 'data.txt' ), '%s' ) ;
 data = reshape( str2double( data{1} ), 17, [] ).' ;
 data = data(:,~isnan( data(1,:))) ;

Then it is possible to split into two blocks if you prefer, for rows "1" and rows "2".

PS: it would be possible to extract non-numeric data as well if you needed.

[Jesus Christian]

hello thank you for your help!

i got this error:

"Error using reshape Product of known dimensions, 17, not divisible into total number of elements, 29099.

Error in Hw5 (line 14) data = reshape( str2double( data{1} ), 17, [] ).' ;

[Cedric]

There is a discrepancy that is not present in the slice that you gave above. If it is not too confidential you can send me the file at [e-mail] and I can have a look tomorrow. Otherwise I can think of a way to investigate (tomorrow).

In the meantime, do you get the same error if you replace the first line of code by

 data = strsplit(strtrim(fileread('data.txt'))) ;

[Cedric]

There is a discrepancy after line 1500. I copied lines 1499 to 1502 here:

 1 25544U 98067A   16136.69611507  .00005252  00000-0  85076-4 0  9996
 2 25544  51.6433 220.1152 0002135 107.8767 350.8535 15.54602232999921
 1 25544U 98067A   16137.21209581  .00005359  00000-0  86643-4 0  9999
 2 25544  51.6435 217.5406 0002111 109.7961 358.5795 15.54608822    13

You can see that lines 1499 and 1500 follow the 9-8 columns pattern present from the beginning of the file, but that lines 1501 and 1502 are 9-9. In fact, from line 1502 on, you loose regularity. The plot below shows the # of elements per line:

You can see that it is regular (dense) 8-9 until 1502. It seems that there are other, minor discrepancies in your data set. Sometimes there is a + in front of positive numbers, sometimes not. Sometimes there is a minus (do you really have negative values?). Also, looking at values between the 8 and 9 values versions of lines with ID 2, it seems that this is a filling problem:

 2 25544  51.6433 220.9943 0002124 108.0375  83.7509 15.54599868999892
 2 25544  51.6433 220.9943 0002124 108.0375  83.7509 15.54599868999892
 2 25544  51.6433 220.1152 0002135 107.8767 350.8535 15.54602232999921
 2 25544  51.6435 217.5406 0002111 109.7961 358.5795 15.54608822    13
 2 25544  51.6440 215.8562 0001995 108.3968  92.4187 15.54614828    61
 2 25544  51.6440 215.8562 0001995 108.3968  92.4187 15.54614828    61

You'll have to understand what is going wrong data-wise, and then we can find a way to process/import the content.

Here is how I looked up for the discrepancy by the way:

 >> rows = strsplit( strtrim( fileread( 'iss.txt' )), '\n' ) ;
 >> rows = cellfun( @strsplit, rows, 'Unif', false ) ;
 >> rowSz = cellfun( 'length', rows ) ;
 >> plot( rowSz ) ;
 >> pos = strfind( rowSz, [9,9] ) ; % Look for first break of [9,8] pattern.
 >> pos(1)
 ans =
        1501

[Jesus Christian]

there are discrepancies but i cannot edit the text file how would I get around this?

[Walter Roberson]

Looks to me as if possibly some of the fields are fixed width -- that perhaps none of the lines are only 8 fields and instead the fields are running together. If so, then that second last field can be handled with %.12f

[Cedric]

You have at least to understand the structure of the data that you are reading, and tell us if, as Walter suggests, there are 9 columns everywhere with fixed width or if it is something else. That must be documented somewhere, and especially the length of the last field.