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importdata - HELP MEMORY

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Linford Briant
Linford Briant 2012-1-25
I am trying to use importdata to import a .dat file which is approximately 349000KB in size. If I import about 75% of the data, MATLAB keeps his cool... but when I try to import the whole things he gets angry and tells me:
N=importdata('Respiratory_Modulation.dat',' ',1);
??? Error using ==> importdata at 214 Unable to load file. Use TEXTSCAN or FREAD for more complex formats.
Caused by: Error using ==> fileread at 36 Out of memory. Type HELP MEMORY for your options.
Why is he angry with me? What have I done?
Thanks,
Linford
  1 个评论
Eric
Eric 2012-1-25
What happens when you try to create a single variable of this size? For instance, try
A = ones(6700,6700);
(don't forget the semicolon!). If this fails then there really does seem to be a memory issue rather than a problem reading in the DAT file.

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采纳的回答

Andreas Goser
Andreas Goser 2012-1-26
Like mentioned in an other answer. A 64 Bit MATLAB on a 64 Bit machine should be tested.
There are however many smart methods to reduce memory. And very often the method depends on your data and application.
In this case, I assume, your data is of type DOUBLE and as you are more than halfway through importing, I like suggesting to convert the data into SINGLE. Most applications do not need DOUBLE data. But as I said, it depends what you do after the data is imported and how often you need to import new data sets.
Assuming, you like to try it:
  • Cut the data into half
  • import it
  • Convert it using SINGLE()
  • save it
  • Do it with the other half
  • Import both

更多回答（2 个）

Walter Roberson
Walter Roberson 2012-1-25
Not very many systems can store 349 gigabytes of data in RAM. Are you certain you need to load all 349 gigabytes at one time??
Linford Briant
Linford Briant 2012-1-25
I'm not being persnickerty, but you may have misread: don't you mean 349 megabytes? I guess they are quite long simulations, but I wouldn't have thought MATLAB would be limited to this.. or, as you said, perhaps its a limitation of my laptop. You are right though, I can possibly split the file up, and do the analysis in chunks. A bit of an inconvenience though!
Any other suggestions?
  2 个评论
Walter Roberson
Walter Roberson 2012-1-25
Sorry, yes, I was off by a suffix.
Walter Roberson
Walter Roberson 2012-1-25
Just before the importdata() call, for debugging please put in a call
memstats
to see how much memory your system has and how much is available.
(Note: this is only valid for MS Windows.)
Are you using a 32 bit version of MATLAB or a 64 bit version? Would switching to a 64 bit version be practical on your system?

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