how to open *.txt files with variable names

Asked by zahra matlab on 13 Oct 2014

Latest activity Edited by Stephen Cobeldick on 4 Mar 2019

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hi I have a function '[dl]=funcall(x,y)' and in it I want to create *.text file with variable names and write out put vectors 'dl'. such as this

    function [dl]=funcdl(x,y)
    .........
    fid=fopen('DL.txt', 'wt');
    fprintf(fid, '%f\n',dl);
    fprintf(fid, '\n');
    fclose(fid);
    ......

but every time by calling function it creates the same name 'DL.txt' and overwrites out put!!! any one can help me???

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2 Answers

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Stephen Cobeldick 님의 답변 13 Oct 2014

Stephen Cobeldick 님이 편집함. 13 Oct 2014

채택된 답변

If you are talking about creating files with sequential filenames, these might be helpful to read:

http://www.mathworks.com/matlabcentral/answers/57446-faq-how-can-i-process-a-sequence-of-files

http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

1 Comment

Stephen Cobeldick 13 Oct 2014

Try this, for example:

for k=1:3
    str = sprintf('temp%d.txt',k);
    fid = fopen(str,'wt');
    ...
    ... write data to your file here (fprintf, or whatever...)
    ...
    fclose(fid);
end

EDIT: uses sprintf, based on the comments of Image Analyst and Robert Cumming.

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Answer by Gaurav Shukla on 13 Oct 2014

Consider an array

VarName = [A,B,C];

for i=1:3
str = strcat('fopen(''',VarName(i),'.txt','wt');
eval(str);
end

14 Comments

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Stephen Cobeldick 13 Oct 2014

The code that Gaurav Shukla wrote includes this line:

str = strcat('fopen(''',VarName(i),'.txt','wt');

However it is wrong code: that string, when evaluated, produces an error, as it is also missing the closing bracket. Did anyone spot this? Was it easy to see, or is it obfuscated in the middle of the ton of brackets and quotation marks? Perhaps they also noticed that this string has the wrong number of quotation marks? More likely they lost track trying to figure out how many quotation marks it needs, just like its author did.

Two major syntax errors in one line of code, due to the obfuscation allowed by using eval. If the function had been called directly, then MATLAB's code editor would simply highlight these coding errors, but it can't do that here because the code is obfuscated in a string: unfortunately the code was NOT actually "easier to immediately understand and see the intent of"! What a shame that its author could not use any of MATLAB's automatic code hinting, could not rely on the syntax checking in the editor, and could not press the F1 key to bring up the help for the function that they were currently typing...

For those who are curious, the error occurs only when the eval statement is called:

>> eval(str);
Error: A MATLAB string constant is not terminated properly.

There is no indication where, or on which line, or in what function this error occurs, or how I could try to find it and fix it... how does this support the argument that "for this one off example, eval is a fast, simple, effective, clear solution" when it doesn't work and it isn't clear how to fix it?

Good coding doesn't depend only on "plans for future use", but making the best use of all of MATLAB's tools and help, including optimizing, debugging, mlint, etc.

There is no better day than today to start learning good coding practices.

Andrew Reibold 13 Oct 2014

You don't have the experience to come up with a single example? Or is this just an attempt at rhetoric..

Stephen Cobeldick 4 Jan 2015

How about this example (from one of your own questions):

http://www.mathworks.com/matlabcentral/answers/157722-title-string1_string2-stop-automatic-subscripts

In a comment to one of the answers to that question you write "Its just that the code I inherited is just an absolute catastrophe when it comes to formatting and practice".

This seems to contradict your earlier comment on this thread: "I'm all for good coding practice, but at the same time when you need a fast, effect, simple, easy to understand solution for a quick job, sometimes being an elitist about your code is more of a hinderance and bottleneck then anything else".

And yet it seems that someone else's "fast, effect[ive], simple" solution became your "absolute catastrophe" problem to solve, which really did cause you a "hinderance and bottleneck" : not because it was well written code, but because it was poorly written code and because this is usually what poorly written and obfuscated code does.

MATLAB's inbuilt tools help to avoid basic syntax mistakes, which goes part of the way to writing good code. So, dear reader, why not use them?

Stephen Cobeldick 4 Jan 2015

For new readers, read all of these comments and

Do NOT use this code

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