is there fast way for this problem

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huda nawaf 2012-1-9

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关闭： MATLAB Answer Bot 2021-8-20

hi, is there a fast way to deal with this problem:

I have 17770 files, each file has structure as:

id_user(integer), rate(integer),date

each file has unique id_user but may share these id_users with other files.

what I want is: each unique id _user be row in array such as: id_user1: rate1 date1 rate3 date3......raten daten id_user2: rate3 date3..rate20 date20........... etc..

I mean rate1 for ex. is rate of user1 in file 1 and rate3 in file 3 and so on. where id_user1 for ex. be in file 1 and file 3 id_user2 be in file 3 and file 20

I wrote code , it is work correctly, but very very slow, it need three hours to creat array with just 50 id_users(read all 17770). I have 480000 id's of users,I have to look for their ratings in 17770 files. I placed my files in folder, then read it one after one. I looked for unique id of users ,then use function (find)in all 17770. Each time looked for id of 30 users as ex. n all files ,then record their ratings in array , but this process take long time, where to accumulate data for 30 users take three hours .

any suggestions, advices may help me

thanks in advance

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Robert Cumming 2012-1-9

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are you preallocating? use the profiler to help locate the time where the code takes longest

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Run on a subset of your files for testing - then expand to include more files.

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huda nawaf 2012-1-11

i can not konow the no. of columns because the code itself will accumulate the the information from all files ,

see

u1 id-mv1 id-mv2.......unknown how many id-mvs

u2 id-mv1 id-mv2 id-mv3............

the id's for each users unknown, also i can not guesses largest no. of id-mv.

regarding dtstr2dtnummx, i got if from the link:

http://www.mathworks.com/matlabcentral/fileexchange/28093-datestr2num, and added it manually.

thanks

Robert Cumming 2012-1-11

either preallocate tobigger than you need and check that it does not grow - or do a preloop to determine size. it will speed things up.

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