Read text file into matlab

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Karthik
Karthik 2015-7-17
编辑： bim 2022-12-25
Hi, I am using the following command to read the text file into matlab.
s=importdata('file.txt');
data=s.data;
text=s.textdata;
colheaders=s.colheaders;
Its working for large data sets. But, its not working for small data sets where I have only 30 data points after the text ends. Can you let me know how to fix it ?
Even its failing to read the attached file. See text file attached.
Thanks.

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回答（2 个）

arun
arun 2015-7-17
编辑：arun 2015-7-17
Sry I don't know why that was not working you can try this alternative one:
clc
clear all
fid = fopen('Raw.txt');
format long
cell_data= textscan(fid,'%f%f%f','Delimiter',' ','headerLines',22);
my_data = cat(2,cell_data{:});
fclose(fid);
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arun
arun 2015-7-17
编辑：arun 2015-7-17
Ty, I used '<space>' sir. I hope u never mind this. '<tab>' or '<space>' never create problem in such files.
Karthik
Karthik 2015-7-17
编辑：Karthik 2015-7-17
Hi, Thanks, I also need the numeric data associated with the text in the data file. How can I extract that ?

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bim
bim 2022-12-25
编辑：bim 2022-12-25
I have been using importdata for textfiles, but it is very slow for text unless you rename all the files to '.txt'.
The function below seems to do the job for structured text files with headerlines specifying nRows and nColumns.
The structure the function can handle is shown at the bottom the function: it only works for tables of float numbers
Let me know whether this works well.
%% READTEXTFILE reads text files without any checks
% READTEXTFILE reads from file and immediately filters out the selectColumns
% READTEXTFILE can read any number of headerlines, but
% the headerlines must contain both nRows='a number' and 'nColumns=a number' in separate lines
% the lines containing nRows and nColumns must not contain any spaces
%
% parameter filename = if the selected file is not a text file, the function will fail
% the extension of the filename is ignored and does not need to be present
% parameter selectedcolumns = header names of columns to be selected from the file
% e.g., selectedcolumns = {'time', 'column_3'}
%
% The read data is returned in a struct c
% content.data = the actual data as a matrix
% content.colheaders = the headers of the remaining columns
% content.colheaders == selectedcolumns
% content.textdata == content.colheaders
%
function content=readtextfile(varargin) % filename,selectedcolumns
tic
selectedcolumns={};
if nargin>2 || nargin ==0
error('readtextfile: too many or too few arguments');
elseif nargin ==2
selectedcolumns=varargin{2};
end
filename=varargin{1};
fid = fopen(filename,'rt');
file.title = fgetl(fid);
file.nrows=string([]);
file.ncolumns=string([]);
line = string(fgetl(fid));
while line ~= "endheader"
if length(file.nrows)==0
file.nrows=regexp(line,'^nRows=(?<nrows>\d+)$','tokens','once');
end
if length(file.ncolumns)==0
file.ncolumns=regexp(line,'^nColumns=(?<ncolumns>\d+)$','tokens','once');
end
line = string(fgetl(fid));
end
file.nrows=str2num(file.nrows);
file.ncolumns=str2num(file.ncolumns);
fsColHeaders = repmat([' %s'],1,file.ncolumns);
colHeaders = textscan(fid,fsColHeaders,1,'EndOfLine','\r\n','MultipleDelimsAsOne',1); % 3rd param (N) == 1 --> read once
fsData = repmat([' %f'],1,file.ncolumns);
fileData = textscan(fid,fsData,'EndOfLine','\r\n','MultipleDelimsAsOne',1); % 3rd param (N) missing --> read until end of file
colHeaders =cellfun(@char,colHeaders,'UniformOutput',false);
[~,copiedColumns] = ismember(selectedcolumns,colHeaders);
if length(copiedColumns)>0
newMatrix= zeros(file.nrows,nnz(copiedColumns));
iNewColumns=1;
for iCopiedColumns = copiedColumns
if iCopiedColumns>0
newMatrix(:,iNewColumns) = fileData{iCopiedColumns};
% newHeaders is not necessary, since it corresponds to selectedcolumns
% but it is is helpful in checking proper operation of the function
newHeaders(:,iNewColumns) = colHeaders(iCopiedColumns);
iNewColumns=iNewColumns+1;
end
end
else
newMatrix = cell2mat(fileData);
newHeaders = colHeaders;
end
fclose(fid);
content.data = newMatrix;
content.textdata = newHeaders;
content.colheaders = newHeaders;
toc
end
% example of possible headerlines
%{
the title
nRows=437
nColumns=17
any number of lines
endheader
time column_1 column_2 column_3 ...
0.001 0.1234 0.3456 0.7891
0.002 0.2234 0.4456 0.8891
%}

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