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Hello MATLAB experts,

I am stuck at a typical problem and would appreciate your help a lot. I am trying to read a complex file(attached - - example.txt). This file has millions of lines I truncated it to only 2000.

My aim is simple:

- If a column is '--- detector1 ---'.
- increament 'numberofgammaclusters'.
- Then X = first numerical digit, Y = second numerical digit, and A(X,Y) = third numerical digit.
- read this till next '--- detector1 ---' is encountered. On the this encounter repeat the steps 2 and 3 are repeated.

The sample code that I am trying is below. Please let me know. Any help regarding the improvements in the code or any advice in the approach is hugely appreciated.

A= zeros(256, 256);

E = importdata('gamma.txt', ' ');

numberofgammaclusters=0;

for i=1:1082952

if E.textdata(:,2)==contains('detector1')

numberofgammaclusters=numberofgammaclusters+1;

A()= % The values at second last column % Part of the code I don know how to write

end

end

Thanks very much in advance.

Regards,

Sanchit Sharma

per isakson
on 30 Jul 2019

Edited: per isakson
on 31 Jul 2019

Try this

%%

chr = fileread( 'example.txt' );

clusters = strsplit( chr, '--- detector1 ---\r\n' );

clusters(1) = [];

clear('chr');

numberofgammaclusters = length( clusters );

A = nan( 256, 256 );

for jj = 1 : numberofgammaclusters

cac = strsplit( clusters{jj},'\r\n' );

for ii = 1 : length( cac )

if not( contains( cac{ii}, '===' ) )

vec = textscan( cac{ii}, 'PixelHit%f%f%f%f', 'Delimiter',',' );

A(vec{1},vec{2}) = vec{3};

else

break

end

end

end

This script requires some memory, but I think it will be ok.

Second thought. Replace

vec = textscan( cac{ii}, 'PixelHit%f%f%f%f', 'Delimiter',',' );

A(vec{1},vec{2}) = vec{3};

by

vec = sscanf( cac{ii}, 'PixelHit%f,%f,%f,%f' );

A(vec(1),vec(2)) = vec(3);

to avoid vec being a cell array

In response to comments

Here is a script that is somewhat more robust. Matlab's indexing is one-based. In your file X and maybe Y takes the value zero. I added "+1".

%%

chr = fileread( 'gamma.txt' );

clusters = regexp( chr, '--- detector1 ---[ ]*\r*\n', 'split' );

clusters(1) = [];

clear('chr');

numberofgammaclusters = length( clusters );

A = zeros( 256, 256 );

for jj = 1 : numberofgammaclusters

cac = regexp( clusters{jj},'\r*\n','split' );

for ii = 1 : length( cac )

if not( contains( cac{ii}, '===' ) )

vec = sscanf( cac{ii}, 'PixelHit%f,%f,%f,%f' );

A(vec(1)+1,vec(2)+1) = A(vec(1)+1,vec(2)+1) + vec(3);

else

break

end

end

end

imagesc( A );

% pick a colormap and show "zero" (approx. A(X,Y)<1) as white

mymap = colormap( parula(1e5) );

mymap(1,:)=1;

colormap( mymap )

colorbar

% flip the YAxis

ax = gca;

ax.YAxis.Direction = 'normal';

outputs

per isakson
on 2 Aug 2019

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Bob Nbob
on 30 Jul 2019

Edited: Bob Nbob
on 30 Jul 2019

I have not been able to utilize your example file, it's a limitation on my end.

That being said, this is how I would look at doing what I understand you're looking for.

fid = fopen('gamma.txt');

line = fgetl(fid);

c = 1;

while isnumeric(line)

if length(line) > 8 & strcmp(line(1:8),'PixelHit')

tmp = regexp(line,' ','split');

A(str2num(tmp{2}),str2num(tmp{3})) = str2num(tmp{4})

end

line = fgetl(fid);

c = c+1;

end

Might need to do some minor editing, because I couldn't use your example file, but the basic concept is sound. If you're looking to capture other data, just add an elseif condition.

This will take some time, but any method (as far as I know) for reading a 2mil line text file is going to take some time.

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