MATLAB: How to Compare value returned by regexp and another string

regexp compare string char strcmp cell

nameF='aa.txt';
cni =regexp (nameF, '.txt', 'split');

I want to compare cni with a String by using strcmp for exemple strcmp(cni,'aa') so I converted its type by using char(cni) since cni is cell but it still returns false even they have the same value. What am I missing here ?

Best Answer

"What am I missing here?" &nbsp I guess you are missing that

cni =regexp (nameF, '.txt', 'split');

returns a &nbsp<1x2 cell> array and that char(cni) returns a &nbsp<2x2 char> matrix

>> nameF='aa.txt';
cni =regexp (nameF, '.txt', 'split')
cni = 
    'aa'    ''
>> char( cni )
ans =
aa
>> double( char( cni ) )
ans =
    97    97
    32    32
>>

instead use

strcmp( cni{1}, 'aa' )

or if 'aa.txt' is a filename

>> [ ~, name ] = fileparts('aa.txt')
name =
aa
>> strcmp( name, 'aa' )
ans =
     1

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MATLAB: Find one of strings into cell array

   find(ismember(cellfun(@(V) lower(char(V)), inputs, 'uniform', 0), cellfun(@lower, {'str1', 'str3', 'str4'}, 'uniform', 0)))

find(any(cell2mat(cellfun(@(c)strcmpi(c,inputs).', {'str1' 'str3' 'str4'}, 'UniformOutput',false)),2))

The first of those has the small flaw that a non-character value that happened to have the same numeric value as a single char target string could be recognized. For example 98 could be matched as if it were 'b'. Also, not everything can be converted to char -- logical cannot, struct cannot.

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

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:

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.
Assigning the result to a structure makes it easy to add more fields. Name and Date are two good candidates for new fields.
With str2num the code does not depend on the number of columns of data.
Structures are easy to make somewhat self-documented
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:

str2num might not be the fastest way to convert to double.
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.

Best Answer

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