Read real numbers with textread

Question

NF 2018-5-4

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此问题的直接链接

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评论： NF 2018-5-4

I have to read specific lines in a .txt file and thus I am using the function textread to do so. The problem is that the lines are composed of real numbers and then textread saves it as '0.957' and not as 0.957 (no commas). Because of that, I cannot save these data into a vector. I tried to remove the commas with regexprep but it didn't work. How can I do that? This is my code (that returns an error):

   clc;
  clear variables;
  close all;
file=fopen('takt_times.txt','r');
nlines=0;
while (fgets(file) ~= -1),
  nlines = nlines+1;
end
fclose(file);
C = textread('takt_times.txt', '%f','delimiter', '\n');
read1=2;
rowindex=1;
a=zeros(40,1);
i=1;
 while rowindex < nlines
     cc=C{read1};
     a(i)=regexprep(cc,"'", "");  
    read1=read1+5;
    rowindex=rowindex+5;
    i=i+1;
 end
a

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Guillaume 2018-5-4

Note: ' is an apostrophe (or a single quote), a comma is ,.

The code in the question differs from the code in your m file. Which do you use? %f will not output '0.957', %s will.

Reading the file twice (once to count the number of lines, once to parse it) is a waste of time. What exactly do you want to extract from the file?

NF 2018-5-4

在 MATLAB Online 中打开

I need to extract and save into a vector some of the numbers in the .txt file, that are distanciated always by the same measure, for example each 6 lines there is the one that I have to save, starting from the third line.

The lines simply are real numbers.

Example:

Line 1
Line 2
Line 3 % save
Line 4
Line 5
Line 6
Line 7
Line 8 % save
Line 9
Line 10
Line 11
Line 12
Line 13 % save
... % and so on

P.S. In the .txt file there are also lines with more thant one value, those lines are not interested in this saving.

@guillaume, yes, there are some differencies in the two because meanwhile I was trying some solutions, however the main code is quite the same. I know the %f and %s thing, I just copied the last trial I had.

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Answer 1

Guillaume 2018-5-4

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Here's how I'd do it:

wholecontent = fileread('takt_times.txt');
lines = strsplit(wholecontent, '\n')';
linestokeep = lines(3:5:end);
numbers = str2double(linestokeep);

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NF 2018-5-4

Thanks, that's perfect

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Answer 2

Ameer Hamza 2018-5-4

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/399026-read-real-numbers-with-textread#answer_318655

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Try using textscan() and specify format using '%f'. It will read the data as floating point numbers.

C = textscan('takt_times.txt', '%f','delimiter', '\n');

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Guillaume 2018-5-4

textread was deprecated many versions ago, but the two are more or less equivalent, the major difference being that textscan returns a cell array wheras textread returns several output.

You should be using textscan instead of textread but just changing the function will have no effect on how the file is parsed.

Ameer Hamza 2018-5-4

@NF, the textscan will load entire and separate into different parts using delimiter. So, in this case, you will get a cell array and each cell contains one line from txt file. It is same as what you will get from textread.

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