Help with writing loop for multiple input files

Question

ajk1 2016-5-12

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/283966-help-with-writing-loop-for-multiple-input-files

编辑： ajk1 2016-5-14

Hi, I am having trouble writing a loop that reads multiple .raw files. The input files are 375x223x91 data sets. I have tried to write a for loop for this but have been unsuccessful. The details are:

vol=read_raw8b('Z:\520\ 1.raw'); %import data

Then executes code...

read_raw8b is a function:

function block=read_raw8b(filename)
fid=fopen([filename],'rb');
block=fread(fid,'*uint8','ieee-le');
fclose(fid);

I would like to write a loop that after executing the code for data set '1.raw' it then loops and imports '2.raw', then executes the same code and so on for 52 data sets.

Also I have a variable in the code called 'map' and I would also greatly appreciate if you could let me know how I can increment this so that when it reads '1.raw' and executes the code it stores variable 'map_1' and when it reads '2.raw' and executes the code it stores as 'map_2' and so on.

Thank you

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Stephen23 2016-5-13

编辑：Stephen23 2016-5-13

@ajk1: changing the names of variables in a loop is a really bad idea. While it is possible, it will be slow, buggy, obfuscated code. As Adam already implied, your best option is to simply use one variable and some indexing. Try using a cell array, it is really simple.

Read this thread and all of its links to know more about why you should not dynamically access variable names:

http://www.mathworks.com/matlabcentral/answers/196952-how-to-create-new-variables-in-batches-with-strcat

Read those links carefully! Notice how many expert MATLAB users have clearly written "do NOT create variable names in a loop". Also notice how many beginners keep inventing this idea!

Many beginners believe that defining or accessing variables in a loop would be a great idea. It isn't. It is a bad way to write code.

Just use one variable and some indexing.

ajk1 2016-5-13

Will do, thank you for your help.

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Answer 1

Azzi Abdelmalek 2016-5-12

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/283966-help-with-writing-loop-for-multiple-input-files#answer_221917

在 MATLAB Online 中打开

for k=1:n
   file=sprintf('Z:\520\%d.raw',k)
   vol=read_raw8b(file)
end

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John BG 2016-5-13

编辑：John BG 2016-5-13

在 MATLAB Online 中打开

I completely agree with Azzi,

don't listen to that chachara of 'don't create variables in loops' without showing you consistent evidence.

If it works and the delay is acceptable, you pack it and you sell it, next one please, if you understand what I mean.

So, on the loop, just one correction, with Azzi's permission, instead of sprintf try

L1='Z:\520\';
for k=1:52
   file=strcat(L1,char(k+48),'.raw')
   vol=read_raw8b(file)
end

and because you said you have up to 52 files, and you may want to have them listed in alphabetic order, you may want to consider naming them 01.raw 02.raw ..

so, you may want to insert in Azzi's loop the following:

L1='Z:\520\';
for k=1:52
  if k<10
     file=strcat(L1,'0',char(k+48),'.raw'); 
     else 
         file=strcat(L1,char(floor(k/10)+48),char(rem(k,10)+48),'.raw'); 
  end
vol=read_raw8b(file)
end