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round off in matlab

Asked by dav on 5 Apr 2013

Hi,

I am running a large simulation in matlab. I have noticed that matlab rounds off after 4 decimal places and this affects my results.

Is there a way to give a command at the beginning of the program so that matlab does the round off after about 10 decimal places?

Thanks.

1 Comment

Roger Stafford on 6 Apr 2013

Matlab's 'double' does not round off after four decimals as far as the actual computations are concerned. It is always accurate to about 16 significant decimal digits. It's only the display of its results that is given to four digits if you are using format short. It is important to understand the difference.

Try this experiment.

 format short
 x = pi^2
 fprintf('x = %19.16f\n',x)

The second display is accurate to 16 places which means that this was the accuracy of the original computation. The 'short' format only displayed four of the significant digits.

dav

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1 Answer

Answer by Azzi Abdelmalek on 5 Apr 2013
Accepted answer
 format long

2 Comments

dav on 5 Apr 2013

thanks

should you put a ";" after this command?

And is there a way to specify the number of decimal places?

Azzi Abdelmalek on 5 Apr 2013
a=0.1234567891011  
sprintf('%.10f',a)
Azzi Abdelmalek

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