Write to file inside a loop

18 次查看（过去 30 天）
Ali Rafiei
Ali Rafiei 2019-7-2
评论： Rik 2019-7-4
I have a loop that each time generates a value 'b1'. I want to create a matrix of all the b1 values to make a histogram at the end. The code that I found is:
q = b1;
save('pqfile.txt','q','-ascii');
this code overwrites and only the last b1 is saved on pqfile. wondering if anyone can help me not overwrite
Thanks
  1 个评论
Rik
Rik 2019-7-4
@Ali, did either answer solve your issue? If so, please consider accepting the answer that works best for you, or comment with your remaining questions.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（2 个）

infinity
infinity 2019-7-2
编辑：Rik 2019-7-2
Hello,
You can refer a simple solution as follows
saveb1 = [];
for (your loop)
your code to compute b1;
saveb1 = [saveb1; b1];
end
save('pqfile.txt','saveb1','-ascii');
In this method, you will save b1 of each loop to a varible saveb1. After the loop, you can save "saveb1" to the text file.
Rik
Rik 2019-7-2
Or a much better practice: if you know the number of iterations you should pre-allocate your output array.
saveb1 = zeros(1,k);
for n=1:k
%your code to compute b1 goes here
saveb1(k)=b1;
end
Alternatively, if you insist of using a file write:
%prepare an empty file
fid=fopen('saveb1.txt','w');
if fid==-1
error('file could not be opened')
end
for n=1:k
%your code to compute b1 goes here
fprintf(fid,'%.1f\n',b1);
end
fclose(fid);
And now you can read the file with all the b1 values.
  2 个评论
Ali Rafiei
Ali Rafiei 2019-7-2
Thank you for your quick answer. The functon that generates b1 already has multiple loops. I was wondering if all of the loops should go into the loop you suggested above?
Rik
Rik 2019-7-2
Yes it would. There might be more efficient options, but simply pasting the code that generates a value for b1 for a given value of n into that loop should do the trick. If it is a slow process you could use the file write (or a normal save/load) to check which values have already been calculated and fill those empty slots.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by