Is it possible to change customization of textscans when importing data from files, in-line?

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Tolulope
Tolulope 2012-9-3
If I want to import the lines from a data file (shown below) with a custom delimiter - then I want to change the delimiter in-line. I'm textscanning using something like this:
fid = fopen('Test2.txt','r');
H = textscan(fid, '%s',21,'delimiter','=');
F = textscan(fid, '%f %f %f %f %f %f %f');
fclose(fid);
The problem is I would like to read in the numbers under Parameter 1 and Parameter 2 as datasets/arrays. I've tried calling them from the cell array, but the result comes out as an array of characters. Is there a way of getting those parameters out as normal arrays using textscan preferences or otherwise?
DATA
Name=Datablock 1
Date=12:02 03/09/2012
Parameter 1=32, 346, 634, 5467, 4567
Parameter 2=6.53; 7.53; 7.67; 9.01; 10.67
Offset=0
Configuration=10
Noise=0.1
Reference number=14546757
Version number=WERGXX1.0a
Alias=False
EOH
0 12341 12341234 34 7 8 446
0 12341 12341234 34 7 8 446
0 12341 12341234 34 7 8 446
0 12341 12341234 34 7 8 446
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Jan
Jan 2012-9-3
@Tolulope: It is not clear what you want to import in which format. Please post, what you expect as output for the given text file.
Tolulope
Tolulope 2012-9-4
编辑：Tolulope 2012-9-4
@Jan trying to answer your question helped me realize the solution to my problem :) I had been trying to scan whole lines of text as one format only. So using the code I gave above, the first 3 lines are...
Name=Datablock 1
Date=12:02 03/09/2012
Parameter 1=32, 346, 634, 5467, 4567
...6 stings separated by " = ". But this converts {32, 346, 634, 5467, 4567} into a character array. I hadn't realized I can simply treat the first three lines as: 5 strings delimited by " = "; 5 numbers delimited by " , "; then one string; then 5 numbers separated by " ; " and so on... I'm now using,
fid = fopen('Test2.txt','r');
H = textscan(fid, '%s',5,'delimiter','=');
F = textscan(fid, '%f %f %f %f %f','delimiter',',');
% and so on ...
fclose(fid);

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per isakson
per isakson 2012-9-4
编辑：per isakson 2012-9-4
If the file fits in memory this is one way to do it.
I decided in some cases what is best for OP;-) and guessed that "EOH" stands for end of header. I missed the meaning of: "... I want to change the delimiter in-line."
Some reasons I do it this way:
  1. The code may be developed one cell at a time in debug mode. I use the "Evaluate cell" button in the toolbar. I check intermediate results before proceeding to next cell.
  2. Assigning the result to a structure makes it easy to add more fields. Name and Date are two good candidates for new fields.
  3. With str2num the code does not depend on the number of columns of data.
  4. Structures are easy to make somewhat self-documented
  5. It is easy to insert a new cell, in which problems are fixed with some find&replace, e.g. convert decimal separator, ',', to '.' and change list delimiters so that str2num can handle the strings.
I often regret that I did not make the code more robust to small changes in the data file.
Test with the small data sample:
>> S = cssm()
S =
Parameter_1: [32 346 634 5467 4567]
Parameter_2: [5x1 double]
Data_block: [4x7 double]
where cssm.m contains
function S = cssm()
fid = fopen( 'cssm.txt', 'r' );
cac = textscan( fid, '%s', 'Delimiter','\n' );
fclose( fid );
cac = strtrim( cac{:} );
ixe = find( strcmp( cac, 'EOH' ) );
cah = cac( 1 : ixe );
cad = cac( ixe+1 : end );
is1 = strncmp( cah, 'Parameter 1', 11 );
is2 = strncmp( cah, 'Parameter 2', 11 );
assert( sum(double(is1))==1 ...
, 'cssm:IllegalNumber' ...
, 'No parameter 1 "%f"' ...
, sum(double(is1)) )
assert( sum(double(is2))==1 ...
, 'cssm:IllegalNumber' ...
, 'No parameter 2 "%f"' ...
, sum(double(is2)) )
buf = regexp( cah{is1}, '=', 'split' );
S.Parameter_1 = str2num( buf{2} );
buf = regexp( cah{is2}, '=', 'split' );
S.Parameter_2 = str2num( buf{2} );
S.Data_block = str2num( char( cad ) );
end
and where cssm.txt contains
Name=Datablock 1
Date=12:02 03/09/2012
Parameter 1=32, 346, 634, 5467, 4567
Parameter 2=6.53; 7.53; 7.67; 9.01; 10.67
Offset=0
Configuration=10
Noise=0.1
Reference number=14546757
Version number=WERGXX1.0a
Alias=False
EOH
0 12341 12341234 34 7 8 446
0 12341 12341234 34 7 8 446
0 12341 12341234 34 7 8 446
0 12341 12341234 34 7 8 446
.
Next task is to profile the code with real data files:
  1. str2num might not be the fastest way to convert to double.
  2. Splitting the content of the file in header, cah, and data, cad, is a bit of a waste of memory and cpu if the data files are large.
  2 个评论
Tolulope
Tolulope 2012-9-4
Yes quite right. Even the code I have is intolerant to any change in the original format. What I eventually did was by brute force: Read every unique recurrence independently. So I have like 10 lines of "textscan"! At least that way I can control how MatLab reads the variables in. Although, I hadn't realized one could use,
S.Data_block = str2num( char( cad ) );
I thought up till now, once a variable becomes a character it can't be turned back into a number of any kind? Thanks for the feedback. Very handy.
per isakson
per isakson 2012-9-4
There are several different functions, which convert from string to numeric, e.g.
C = textscan( str, ... )
A = sscanf( str, format, sizeA )
X = str2double('str')

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