convert binary to charaacter

2014 8 15
2 个回答
回答已采纳
更新时间：2014 8 16
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0 个投票

hello,
i have a binary sequnce 10110001. and i want to encode based on the following rule
A=00
C=01
T=10
G=11
and the answer i get will be something like TGAC.
i want to do it for a 256*256 matrix each element having an 8bit binary sequence..i have generated the matrix by using the following code
>>a=imread('C:\Users\Abzz\Desktop\lena.png');
>>disp(a);
>>imshow(a);
>>for i=1:1:256
>>for j=1:1:256
>>b{i,j,1} = dec2bin(a(i,j),8);
>>end
>>end
>>disp(b)
pls help..thanks in advance

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Guillaume
Guillaume 2014-8-15
编辑：Guillaume 2014-8-15

2 个投票

Personally, if I was going to do that encoding several times, I would precompute the encoding for all the possible values (there's only 256 of them) and use the precomputed array to do the conversion using basic matrix indexing. Thus the expensive calculation you only do once and the conversion from matrix to sequence is a simple array lookup, thus very fast.
You can precompute the array many different ways. A fairly simple one:
sequences = 'ACTG'; %in the order 0,1,2,3
seqbase4 = dec2base(0:255, 4); %convert integer 0-255 to a sequence of 0123
int2sequence = num2cell(sequences(seqbase4-'0'+1), 2); %represents integer 0-255 as cell array of ACTG
Whenever you want to convert a matrix, it's then as simple as:
a=imread('C:\Users\Abzz\Desktop\lena.png');
s=int2sequence(a+1); %+1 because matlab indexes start at 1

更多回答（1 个）

Azzi Abdelmalek
Azzi Abdelmalek 2014-8-15
编辑：Azzi Abdelmalek 2014-8-15

0 个投票

str='10110001'
c='ACTG'
b={'00','01','10','11'}
ss=regexp(str,'.{2}','match')
[ii,jj]=ismember(ss,b)
out=c(jj)
%or
str='10110001'
c='ACTG'
out=c(bin2dec(regexp(str,'.{2}','match'))+1)
%or
str='10110001'
c='ACTG'
out=c(bin2dec(reshape(str,2,[])')+1)

10 个评论
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Abirami
Abirami 2014-8-15
sir i understood the concept but i don't know how to apply it for the matrix..if i employ a loop im getting it wrong..pls help..
Azzi Abdelmalek
Azzi Abdelmalek 2014-8-15
How is your matrix? give a short example
Azzi Abdelmalek
Azzi Abdelmalek 2014-8-15
M={'10110001','10010010'} % Your matrix
str='10110001'
c='ACTG'
out=cellfun(@(x) c(bin2dec(reshape(x,2,[])')+1),M,'un',0)
Abirami
Abirami 2014-8-15
编辑：Abirami 2014-8-15
a={'00111011' '01110011' '11011101' '10110111'} sir this is just a sample. imagine a 256*256 matrix.
Guillaume
Guillaume 2014-8-15
Did you matrix starts out as binary strings or as integer? If the latter, you don't need to convert to binary (which is the wrong base anyway, you're operating in base 4 not base 2)
Abirami
Abirami 2014-8-15
No sir initially the matrix is a decimal valued one which i convert to 8bit binary sequence..
Guillaume
Guillaume 2014-8-15
Then see my answer. You have all the steps there.
Abirami
Abirami 2014-8-16
still not getting it sir..i'm new to Matlab so im not able to understand it easily..can u pls elaborate sir so that i correct my code...
Guillaume
Guillaume 2014-8-16
Have you tried what I wrote in my answer? Does it not work for you? If it doesn't, which step is the problem?
Azzi Abdelmalek
Azzi Abdelmalek 2014-8-16
编辑：Azzi Abdelmalek 2014-8-16
a=imread('C:\Users\Abzz\Desktop\lena.png');
[n,m]=size(a);
b=arrayfun(@(x) dec2bin(x,8),a,'un',0);
c='ACTG';
out=cellfun(@(x) c(bin2dec(reshape(x,2,[])')+1),b,'un',0)
Note that Guillaume's method is faster, and do not need to convert your matrix from decimal to binary

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