Randomly accessing a file from a folder using Matlab

KT
2012 4 13
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I am trying to randomly access a file from a folder using matlab, could you suggest me that how shall i go about, i am planning to use randn function? but i dnt understand i shall i merge it !

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Geoff
Geoff 2012-4-13

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I understand your question in two different ways:
1. You want to choose a random file from a specified folder
2. You want to choose a random position in a single file in a folder.
I use randi here, but if you want to use randn you probably need to find a way to turn that into an integer. It's unusual to want to use a normal distribution for something like you seem to be describing though.
So...
If (1) Use the dir command to list files in that folder:
f = dir( myfolder );
ridx = randi(numel(f));
disp( ['Chosen file is: ' f(ridx).name] );
If (2) Open your file and determine its size, then seek to random position:
fid = fopen( myfile, 'rb' );
fseek(fid, 0, 'eof' );
fsize = ftell(fid);
rpos = randi(fsize)-1;
fseek(fid, rpos, 'bof');
...
fclose(fid);

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KT
KT 2012-4-13
yes i wanted to do what you mentioned in your option 1 , thank you so much,could you tell me that i have 5 files in my folder, but when i use *numel* , it gives 7 instead of 5, where two files were turning out to be in the form of *..* so do you know the reason for it?

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