Concatenating binary bits into a number

Question

I want to concatenate last four bits of binary into a number i have tried the following code

x8=magic(4)
x8_n=dec2bin(x8)
m=x8_n-'0'

which gives me the following output m =

     1     0     0     0     0
     0     0     1     0     1
     0     1     0     0     1
     0     0     1     0     0
     0     0     0     1     0
     0     1     0     1     1
     0     0     1     1     1
     0     1     1     1     0
     0     0     0     1     1
     0     1     0     1     0
     0     0     1     1     0
     0     1     1     1     1
     0     1     1     0     1
     0     1     0     0     0
     0     1     1     0     0
     0     0     0     0     1

now i want to take every last 4 bits it each row and convert it into an integer

Luis Mendo · Accepted Answer · 2014-03-31 16:18:03Z

3

n = 4; %// number of bits you want
result = m(:,end-n+1:end) * pow2(n-1:-1:0).'; %'// matrix multiplication

Anyway, it would be easier to use mod on x8 directly, without the intermediate step of m:

result = mod(x8(:), 2^n);

In your example:

edited Mar 31, 2014 at 16:18

answered Mar 31, 2014 at 16:12

Luis Mendo

113k13 gold badges80 silver badges154 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Divakar Over a year ago

+1 for a complete answer BTW :) OP won't need all those three lines to get to m

Divakar · Accepted Answer · 2014-03-31 16:16:55Z

2

This could be another approach -

n = 4; %%// number of bits you want
out = bin2dec(num2str(m(:,end-n+1:end)))

Output -

answered Mar 31, 2014 at 16:16

Divakar

222k19 gold badges273 silver badges374 bronze badges

3 Comments

Luis Mendo Over a year ago

Or, more simply, out = bin2dec(x8_n(:,end-n+1:end)) :-) +1

johnny Over a year ago

what if i want to take the middle two bits of the m array ?

Divakar Over a year ago

This must work for that case - out = bin2dec(num2str(m(:,3:4))). It's all about manipulating the second index of m, which denotes the column number(s).

Collectives™ on Stack Overflow

Concatenating binary bits into a number

2 Answers 2

1 Comment

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related