How to reduce the time?

Question

Shifat 2012-3-1

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Hi. I am trying to convert a decimal matrix in to binary form by using following code:

            k = 1;  
            P = '';                %%P is the output matrix
            for i = 1 : numel(s)  %%s is the input matrix
                P(k,1:bin_total) = bin(fi(s(i),1,8,6)); 
                                   %%Decimal to binary conversion
                k = k+1; 
            end

I am trying to reduce the time because the input matrix may have 1000 elements. So it's taking very long time for converting in to binary.

Can anyone please give me any idea how to make the code more faster?

Thanks.

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Walter Roberson 2012-3-7

Okay -- signed or unsigned?

Shifat 2012-3-7

Signed.

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Answer 1

Laurens Bakker 2012-3-7

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Hi Shifat,

the base MATLAB distribution has a function for this:

P = dec2bin( fix(s) );

where fix() cuts off the fractional part. Let me know if this is not fast enough for you. There are some faster ways of doing it, but that gets somewhat involved.

Cheers,

Laurens

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Shifat 2012-3-7

Thank you for your help.

But i need the fractional part too and the also need the bit system be fixed (Like 6 bits for fractional part and 2 bits for integer part.)

I found some thing which seems to me more faster than my previous 'for loop'code (which i posted above):

P = bin(fi(decimal_input_matrix,1, 8, 6)) %8 represents whole binary number and 6 represents the length of fractional part

I found that this code takes almost less than half time if i don't use loop.

If you have anything which works more faster than this, please let me know. Thanks.

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Answer 2

Shifat 2012-3-10

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I am deleting my other post which contains the same subject. Jan Simon answered in that question which helped me a lot. Following answer was given by him:

Pre-allocation!

   k = 1;  
   P = repmat(' ', numel(s), bin_total);
   for i = 1 : numel(s)  %%s is the input matrix
      P(k, :) = bin(fi(s(i),1,8,6));
      k = k+1; 
   end