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retrieve binary data back

Asked by Elysi Cochin on 17 Mar 2019
Latest activity Commented on by Rik
on 18 Mar 2019
I have a binary data as
00 10 11 01 10 11 11 01
I need to replace this data as if
00 = 0
01 = 1
10 or 11 = *
if i get a new data as below
0 * * 1 * * * 1
can you suggest any way to get back the binary data
00 10 11 01 10 11 11 01

  1 Comment

Rik
on 17 Mar 2019
Because your mapping is not unique, this is not possible. There is no way for the reverser to know if you * was 10 or 11, so it will not be able to return a perfect reconstruction.
Also, cryptography is a bit of a tricky subject on this website, see the discussion here.

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3 Answers

Answer by Rik
on 18 Mar 2019
 Accepted Answer

In case you wanted to accept my answer, I'll repost my code in an actual answer. However, I would suggest you use Madhan's solution. That one ignores the last bit if the length is odd (which might not be what you want), while my code throws an error.
data='0010110110111101';
replace_with={'00','0';'01','1';'10','*';'11','*'};
key_list=replace_with(:,1);
val_list=replace_with(:,2);
%check for even numbers:
if rem(numel(data),2)~=0
error('bits are not paired')
end
%convert to 1 pair per cell
datacell=mat2cell(data,1,2*ones(numel(data)/2,1));
% %loop through the replacer elements
% for n=1:numel(key_list)
% datacell(ismember(datacell,key_list{n}))=val_list(n);
% end
inds=cellfun(@(x) find_indices(x,key_list),datacell);
L= inds~=0;
datacell(L)=val_list(inds(L));
%convert back to a char array
result=cell2mat(datacell);
clc,disp(result)
%local function:
function inds=find_indices(element,key_list)
[~,inds]=ismember(element,key_list);
end

  3 Comments

Rik
on 18 Mar 2019
I mean that if you enter an odd number of bits, my code will throw an error:
data='011';
Error using Untitled (line 7)
bits are not paired
And Madhan's code will ignore the last bit and only process '01':
D =
'1'
Thank you sir
Sir is it possible to get back the data
data='0010110110111101'
from result = '0**1***1'
through any method
Rik
on 18 Mar 2019
No, that reversal is not possible, unless there is a known pattern to your data.

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Answer by madhan ravi
on 18 Mar 2019
Edited by madhan ravi
on 18 Mar 2019

c=strjoin(regexp(c,'\d{2}+','match')); % for safety measure
% ^----- your original binary data
Actual_datas={'00','01','10|11',' '};
Replace_with={'0','1','*',''};
D=regexprep(c,Actual_datas,Replace_with)

  0 Comments

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Answer by Image Analyst
on 17 Mar 2019

Use strrep(). Try this:
str = '00 10 11 01 10 11 11 01'
% Make the length a multiple of three.
while rem(length(str), 3) ~= 0
str = [str, ' '];
end
% Make replacements
% 00 = 0
% 01 = 1
% 10 or 11 = *
str = strrep(str, '00 ', '0 ')
str = strrep(str, '01 ', '1 ')
str = strrep(str, '10 ', '* ')
str = strrep(str, '11 ', '* ')
% If desired, trim off any trailing or leading spaces.
str = strtrim(str)

  4 Comments

Show 1 older comment
I'm not really 100% sure if there are actually spaces in it or if she just put them in to make it easier to visualize the pairs of digits. Maybe she'll say.
I find cellfun() is too cryptic for beginners, but if you have an example, please post it.
Rik
on 17 Mar 2019
Judging by the track record of Elysi I wouldn't call them a beginner anymore, but just in case other/future readers need an example (which assumes the spaces are not in the actual data):
data='0010110110111101';
replace_with={'00','0';'01','1';'10','*';'11','*'};
key_list=replace_with(:,1);
val_list=replace_with(:,2);
%check for even numbers:
if rem(numel(data),2)~=0
error('bits are not paired')
end
%convert to 1 pair per cell
datacell=mat2cell(data,1,2*ones(numel(data)/2,1));
% %loop through the replacer elements
% for n=1:numel(key_list)
% datacell(ismember(datacell,key_list{n}))=val_list(n);
% end
inds=cellfun(@(x) find_indices(x,key_list),datacell);
L= inds~=0;
datacell(L)=val_list(inds(L));
%convert back to a char array
result=cell2mat(datacell);
clc,disp(result)
%local function:
function inds=find_indices(element,key_list)
[~,inds]=ismember(element,key_list);
end
sorry sir, what you said is right. There was no spaces
I wrote like that to make it readable. I didnt think the other way. Sorry.
Rik Wisselink Sir your answer is what i wanted.

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