Help with writing loop for multiple input files

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

[Adam]

Why would you want variables map_1 and map_2 instead of just a single variable array containing map(1) and map(2)?

[ajk1]

Hi Adam, thank you for the question. I wanted to have separate variables because later I would like to be able to plot map_1, map_2, etc... as they will be 375x223 size. Also be able to plot them on-top of each other. If I will be able to do that using a single variable array map(1) and map(2) then great, but would need help doing that.

[Stephen23]

@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]

Will do, thank you for your help.

Answer 1

[Azzi Abdelmalek]

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

[ajk1]

Thank you for your help. I edited my question shortly after posting it (adding an additional query below). I would be very grateful if I could get your help with the 'map' variable (as described above). Thank you.

[ajk1]

I tried running the code:

for k=1:52
 file=sprintf('Z:\520\%d.raw',k)
 vol=read_raw8b(file)
% Code to be executed
end

However I received these errors:

Error using fread
Invalid file identifier.  Use fopen to generate a valid file
identifier.

Error in read_raw8b (line 4)
block=fread(fid,'*uint8','ieee-le');

Error in count_cracks_3D (line 3)
  vol=read_raw8b(file);

Please let me know if I am running it incorrectly, I have tried altering the read_raw8b function, using fopen due to the error using fread, however this also did not work. Thanks.

[John BG]

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

John

[e-mail]

[ajk1]

Perfect, the code is working now. Thanks to all that have helped and advised.