How do I determine the number of headerlines in a text document?
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I need to read in data from a text document. The document starts with an unknown number of headerlines (zero up to 20), and the data is broken into two columns with an unknown number of rows.
4 points
PER AREA
1.000000 0.995458
0.997791 0.981313
0.988447 0.980913
0.987217 0.971326
I would like to determine the number of headerlines there are in the document, and then use textscan to skip them. My code so far is...
fileID = fopen('nameoffile.txt');
n = 0;
tline = fgetl(fileID);
while ( ischar(tline) || isinteger(tline) )
tline = fgetl(fileID);
n = n+1;
end
data = textscan( fileID, '%f%f%*[^\n]','Headerlines',n,'CollectOutput',true);
This gives me a header count, 'n', that is equal to the number of lines in the file. Is there a way to do this?
Thanks.
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回答(4 个)
Jos (10584)
2014-6-18
Read the file as strings and parse the strings. The following might work (at least it works when I copied your example into a file.)
DataFile = 'data.txt'
C = textread(DataFile, '%s','delimiter','\n')
V = cellfun(@(s) sscanf(s,'%f%f').', C, 'un', 0)
DATA = vertcat(V{:})
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Jos (10584)
2014-6-18
And to obtain the headers:
HEADER = C(cellfun('isempty',V))
dpb
2014-6-17
TMW has already done it for you...
doc importdata
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dpb
2014-6-18
Doesn't look like should be...and indeed, it worked on that snippet of a file here--
>> josh=importdata('josh.txt')
josh =
data: [4x2 double]
textdata: {6x2 cell}
colheaders: {'PER' 'AREA'}
>> josh.data
ans =
1.0000 0.9955
0.9978 0.9813
0.9884 0.9809
0.9872 0.9713
>>
This is R2012b/32-bit Windows. Your version and if fails consistently on your system would seem to be worthy a bug report.
Joseph Cheng
2014-6-18
编辑:Joseph Cheng
2014-6-18
Well if you are having arbitrary headers but you know where the data starts (with the column headers PER and AREA); then you can hunt for the start of data using fgetl and strfind. so you'll open the file, fgetl and given certain conditions look for strfind(line,'PER')==1 and the same for AREA (i don't know the line position of AREA). Additionally you can put in a check to see that the data afterwords is 2 numbers if ~isempty(str2num(nextline));
after you get your heading position use that in dlmread.
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Gabriel Felix
2020-5-24
I had to use \n at the end of each line. Without it I couldn't make textscan() work properly, even thoug the "HeaderLines" was configured according to the text file lines. This was the only solution I found after struggling with the code for an intire day.
This was the text:
!
!
! alfa (graus) = 5.0
!
! Id. x/s z/s alfai cl c*cl/cmed cdi cmc/4
! (graus)
1 .246 .050 -1.209 .255 .332 .00538 .0170
2 .292 .150 -1.098 .259 .319 .00496 .0545
3 .339 .250 -.925 .254 .297 .00410 .0944
4 .385 .350 -.741 .243 .268 .00315 .1341
5 .432 .450 -.561 .227 .235 .00223 .1714
6 .479 .550 -.393 .206 .199 .00141 .2034
7 .525 .650 -.238 .181 .163 .00075 .2266
8 .572 .750 -.101 .152 .126 .00027 .2362
9 .619 .850 .014 .116 .089 -.00003 .2236
10 .659 .938 .103 .074 .052 -.00013 .1693
!
! CL asa = .208
! CDi asa = .00258
! e (%) = 88.9
! CMc/4 asa = .1339
My code:
%! alfa (graus) = 5.0
P = textscan(fid,'! alfa (graus) = %f','Delimiter',' ','MultipleDelimsAsOne',true,'headerLines',2,'CollectOutput',1);
alpha(1) = P{1};
%! CL asa = .208
P = textscan(fid,'! CL asa = %f\n','Delimiter',' ','MultipleDelimsAsOne',true,'CollectOutput',1,'headerLines',4+n);
CL(1) = P{1};
%! CDi asa = .00258
P = textscan(fid,'! CDi asa = %f\n','Delimiter',' ','MultipleDelimsAsOne',true,'CollectOutput',1,'headerlines',0);
CDi(1) = P{1};
%! CMc/4 asa = .1339
P = textscan(fid,'! CMc/4 asa = %f','Delimiter',' ','MultipleDelimsAsOne',true,'CollectOutput',1,'HeaderLines',2);
Cmc4(1) = P{1};
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Gabriel Felix
2020-5-25
What an elegant solution! Thank you for helping. I posted it here because I thought it was related to this topic's subject. (This topic was one of the many I consulted for trying to solve my problem).
However I should have made a question with it. I would have done it if I hadn't solved the problem with this less elegant solution.
I really liked your approach. Thanks a lot man!
dpb
2020-5-25
No problem; glad to be of help.
Illustrating some of the newer string class functionality that is useful for such -- even I wasn't sure the lookup syntax was going to work as intended but tried it as being what I knew I wanted! :)
The other really important takeaway is when you have strings for variables, use a struct or a table or one of the similar data structures that has the facility to address the field or variable name within it--don't try to make variables directly that end up with the dreaded eval as only way to use them.
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