# Using randperm to generate a shuffled cell array. How do i get the original ordered cell array

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Kenneth on 2 May 2014
Commented: Kenneth on 2 May 2014
I try to create a trivia-game where the user have to enter F for a false question and T for a true question.
I have a cell array Q containing several strings of questions. To sort Q randomly, I do this:
neworder = randperm(numel(Q));
Qshuffled = Q(neworder)
Using a while-loop I create a cell array R containing -1 for wrong answers given by the user, 0 if no answers is given and 1 for correct answers. Now (naturally) the order of answers in R corresponds to the order of questions in Qshuffled. I now want to re-order R to the same order as Q, so that the answers given by the user can be compared to the original order of questions in Q.
I hope someone can help me. Thanks.
If it helps the While-loop looks like this (A is a logical vector containing 1 for true answer and 0 for false answer)
neworder = randperm(numel(Q));
Qshuffled = Q(neworder);
A = A(neworder);
while run_random == 1 && i <= numofQ
tic
userinput = input([Qshuffled{i} ' '], 's');
switch userinput
case 'T'
if isequal(1, A(i))
R(i) = 1;
else
R(i) = -1;
end
case 'F'
if isequal(0, A(i))
R(i) = 1;
else
R(i) = -1;
end
case ''
R(i) = 0;
case 'Afslut'
break
otherwise
display(' ')
display('Dit input er ugyldigt.')
display (' ')
pause(1.5)
display('Tast:')
display(' ''T'' for sandt udsagn.')
display(' ''F'' for falsk udsagn.')
display(' ''Enter-knappen'', hvis du ikke kender svaret.')
display(' ''Afslut'' hvis du ønsker at forlade testen.')
display(' ')
end
O{i} = Qshuffled{i};
T(i) = toc;
i = i + 1;
else
end
end

Azzi Abdelmalek on 2 May 2014
Example
a={'a' 'b' 'c' 'd' 'e' 'f'}
n=numel(a)
ii=randperm(n)
[~,previous_order]=sort(ii)
b=a(ii)
%to get a
old_a=b(previous_order)
Kenneth on 2 May 2014
oh, i see.
Again, thanks a lot