Identifying a repeating number in a large data file

I am trying to write a function that deals with large amount of data collected from EEG electrodes using EEG lab. I am trying to write a function that finds a number, say 9, in a large data retrieved from the experimental results and i could later use the indexing of these occurring 9s which may or may not occur at the same interval. I would also like to use this indexing of the 9 to be able to do number manipulation with the 9 and 2 numbers to its left and 2 to its right. Anybody got any ideas about the sort of functions that i should look at to achieve this??

Answer 1

[Azzi Abdelmalek]

A function that finds these numbers is find

Example:

A=[1 2 3 9 4 5 6 8 9 10 1 0 5]
idx1=A==9  
idx2=find(A==9)

See also ismember function

[Sanwal Yousaf]

Could you use this to find an number from a http://www.mathworks.com/help/matlab/ref/uigetfile.html function.

Say,i use the uiget function to obtain the file, then could find still be used??

[Cedric]

UIGETFILE will just give you a file name and a directory (as strings). If you do

 [fileName, pathName] = uigetfile( '*.txt' ) ;

you just trigger a file selection window, which returns the location of the file. Then you have to build the full path/locator:

 locator = fullfile( pathName, fileName ) ;

and then read the file content. Depending what format it is, you can use IMPORTDATA, TEXTSCAN, XLSREAD, etc. For example:

 A = xlsread( locator ) ;

After reading the file, and possibly making a few data conversions, you have an array of numbers that you can process the way Azzi explained if you are looking for given exact values.