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Get bits of number.

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Raldi
Raldi on 13 Apr 2015
Edited: Guillaume on 13 Apr 2015
I have a 16 bit double I got from using wavread that I want to get the first 8 bits from.
As an example lets say I have 67. Inside my computer it must be represented as a series of bits, 0111001 in this case. So lets say that I just want to have the last for of them 1001.
How can this be done?
  3 Comments
Raldi
Raldi on 13 Apr 2015
I probably meant 57. Also yeah they are double but I calculated that I only need 16 bits to represent all numbers in that range, all the rest are zeros.

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Accepted Answer

Guillaume
Guillaume on 13 Apr 2015
Assuming you have a 16 bit integer, the simplest way to extract some bits from it is to use bitget:
n = hex2dec('AF75'); %for example, bit pattern is 1010 1111 0111 0101.
bitpattern = bitget(n, 1:8, 'uint16')
returns
bitpattern =
1 0 1 0 1 1 1 0
You can also use dec2bin but that involves string conversion so is going to be slower.
  2 Comments
Guillaume
Guillaume on 13 Apr 2015
I'm not sure when the type specifier was added to bitget, I think it's fairly recent.
On older versions of matlab, this should work:
n = hex2dec('AF75'); %for example, bit pattern is 1010 1111 0111 0101.
bitpattern = bitget(uint16(n), 1:8)
That is convert your number (of type double) to an unsigned integer type.

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