How to combine numerical values into one?
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Hi all
I've got a question for you. Lets say I have two vectors a and b, respectively, with the following content:
a = [0 1 1]
b = [1 0 1]
I wish to combine these with a one-liner (preferably a built-in function) so that I get
c = [01 10 11]
How to go about this? I don't mind if the elements in c are strings.
Your help is much appreciated. Cheers!
1 Comment
the cyclist
on 17 Mar 2015
Is it OK if c is one string? Or do you need three distinct strings, stored in a cell array?
Answers (4)
per isakson
on 17 Mar 2015
Edited: per isakson
on 17 Mar 2015
"I don't mind if the elements in c are strings."   The leading zero in 01 requires a string. Try
>> sprintf( '%1d%1d ', [a;b] )
ans =
01 10 11
or better
>> str = strtrim( sprintf( '%1d%1d ', [a;b] ) )
str =
01 10 11
 
Addendum triggered by comment
>> cac = strsplit( strtrim( sprintf( '%1d%1d ', [a;b] ) ) )
cac =
'01' '10' '11'
>> cac{2}
ans =
10
>>
>> C = textscan( cac{2}, '%1d%1d' );
>> C{:}
ans =
1
ans =
0
or to output strings
>> C = textscan( cac{2}, '%1c%1c' );
>> C{:}
ans =
1
ans =
0
or just
>> cac{2}(1)
ans =
1
>> cac{2}(2)
ans =
0
Guillaume
on 17 Mar 2015
As others have said, the only way you can keep that leading zero is by using strings since leading zero have no meaning with numbers. Using strings is expensive though in term of processing time.
I'm not sure why you can't keep your states as a 2D matrix, in my opinion it's the easiest to manipulate and visualise. If you don't want to keep your states as a matrix, then the next best option would be to keep them as a decimal numbers, since after all your combination of states are just binary representation of numbers. A generic way to convert from your states to a vector of number would be:
fromstates = @(varargin) arrayfun(@(varargin) polyval(cell2mat(varargin), 2), varargin{:});
e.g:
>>fromstates([0 1 1], [1 0 1])
ans =
1 2 3
>>fromstates([0 1 0 1], [1 0 0 1], [1 1 0 0])
ans =
3 5 0 6
>>bitget([3 5 0 6], 2)
ans =
1 0 0 1
Or to get all the states back all at once:
deal2 = @(c) c{:}; %helper function
tostates = @(decvalues) deal2(arrayfun(@(bit) bitget(decvalues, bit), nargout:-1:1, 'UniformOutput', false);
>>[a, b, c] = tostates([3 5 0 6])
a =
0 1 0 1
b =
1 0 0 1
c =
1 1 0 0
If you really want strings, then a generic way to convert to string is:
fromstate = @(varargin) num2cell(char(vertcat(varargin{:}) + '0')', 2)';
>>fromstate([0 1 0 1], [1 0 0 1], [1 1 0 0])
ans =
'011' '101' '000' '110'
And back
deal2 = @(c) c{:};
tostates = @(strings) deal2(num2cell(vertcat(strings{:})' - '0', 2);
>>[a, b, c] = tostates({'011' '101' '000' '110'})
a =
0 1 0 1
b =
1 0 0 1
c =
1 1 0 0
0 Comments
Jos (10584)
on 17 Mar 2015
Use the power of ARRAYFUN:
a = [0 1 1]
b = [1 0 1]
c = arrayfun(@(k) sprintf('%d%d',a(k),b(k)),1:numel(a),'un',0)
a2 = arrayfun(@(k) c{k}(1)-'0',1:numel(c))
b2 = arrayfun(@(k) c{k}(2)-'0',1:numel(c))
0 Comments
Gunnar
on 17 Mar 2015
3 Comments
John D'Errico
on 17 Mar 2015
The problem is, you want to keep the pair [0 1] as a pair. If you convert it to a number, then clearly 01 is just 1. MATLAB does not recognize high order zero bits as adding useful information. This is a property of floating point numbers.
SOOOOO, if you insist on keeping those values together, they cannot be numeric. So you must be willing to either keep them as essentially a 1x2 element array of numbers, or as a string. Those are your choices. And operations on strings are never quite as trivial as they are on numbers.
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