MATLAB: Hello! I need to extract the lines which start with PG10 from this text file. Could you please help me. Thanks! I would use while loop but I am not sure how.

get lines

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Best Answer

fmt=['PG10 ' repmat('%f ',1,8)];
fid=fopen('sp3data.txt');
PG10=[];
while ~feof(fid)
  PG10=[PG10; cell2mat(textscan(fid,fmt,'collectoutput',1))];
end
fid=fclose(fid);
is the "quick-n-dirty" solution. It simply concatenates the next set of values onto the preceding with dynamic reallocation. Presuming there aren't a zillion PG10 records in the file, this will be quick-enough.
If there are so many that performance is slow, preallocate the array as
PG10=zeros(AVERYBIGNUMBER,8);
and populate it by keeping a counter
i=0;  % initialize counter
while ~feof(fid)
  i=i+1;   % increment
  PG10(i,:)=cell2mat(textscan(fid,fmt,'collectoutput',1));
end
fid=fclose(fid);
ADDENDUM
Per the note in comments, the above won't work as is...
fmt=['PG10 ' repmat('%f ',1,8)];
fid=fopen('sp3data.txt');
PG10=[];
while ~feof(fid)
  l=fgetl(fid);        % read a record
  if strfind(l,'PG10')
    PG10=[PG10; cell2mat(textscan(l,fmt,'collectoutput',1))];
  end
end
fid=fclose(fid);
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