MATLAB: How to extract data from strcture

array

if i have a structure of 101 nodes, i want to extract the data of the first 99 nodes only in an array

Best Answer

If you have a structure array of more than 100 "elements", then you can extract the first 99 like this:

s99 = s(1:99);

This will extract the first 99 into another variable, s99, and all "fields" of the structure will also be brought along.

Related Solutions

MATLAB: Array of structures in matlab

array1=1:10
array2=21:30
out=struct('field1', num2cell(array1),'field2',num2cell(array2))

MATLAB: Extracting information from file

This is one way to read the your file

>> tic, sas = nohup, toc
sas = 
1x1173 struct array with fields:
    SampleName
    NumOfCells
    Porosity
Elapsed time is 27.000338 seconds.
>> ix = find( strcmp( {sas.SampleName}, 'cutTDM050_111_121_221_222_122' ) )
ix =
   583
>> sas(ix).Porosity
ans =
    0.0828    0.0828    0.0828
>> sas(ix).NumOfCells
ans =
      125000      125000      125000

where (in one m-file)

function    sas = nohup
%%    
    str = fileread( 'nohup.txt' ); 
%%
    heading_string  = 'Running Sample';
    trailing_string = '=============================================='; 
    %
    xpr = sprintf( '(?<=%s).+?(?=%s)', heading_string, trailing_string );
    cac = regexp( str, xpr, 'match' );
%% 
    sas = struct( 'SampleName',repmat({''},[1,length(cac)]) ...
                , 'NumOfCells',{[]}, 'Porosity', {[]}       );
    for jj = 1 : length( cac )
        sas(jj) = nohup_( cac{jj} ); 
    end
end
function    sas = nohup_( str )
    %
    sas.SampleName ... 
    =   regexp( str, 'cutTDM\d{3}_\d{3}_\d{3}_\d{3}_\d{3}_\d{3}', 'match', 'once' );
    %
    cac = regexp( str, '(?<=Num of cells +\= *)\d+', 'match' ); 
    sas.NumOfCells = str2double( cac );
    %
    cac = regexp( str, '(?<=Porosity +\= *)[\d+\.]+', 'match' ); 
    sas.Porosity = str2double( cac );
end

&nbsp

Comments:

The function is slow. Nearly all the time is spend with regexp searching for "Num of cells" and "Porosity". "the Num of cells and porosity value are the same." may be used improve speed. Adding 'once' to these two calls of regexp increases the speed forty times. That's much more than I anticipated; I don't understand; I cannot see what's taking all the extra time.

>> tic, sas = nohup, toc
sas = 
1x1173 struct array with fields:
    SampleName
    NumOfCells
    Porosity
Elapsed time is 0.645206 seconds.
>> ix = find( strcmp( {sas.SampleName}, 'cutTDM050_111_121_221_222_122' ) )
ix =
   583
>> sas(ix).Porosity
ans =
    0.0828
>> sas(ix).NumOfCells
ans =
      125000
>>

Best Answer

Related Solutions

MATLAB: Array of structures in matlab

MATLAB: Extracting information from file

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