How to substitute one value in vector by vector?

Hello,

I have got a vectro x=(-1 1 -1 1) and I need to replace positions containing -1 for a vector (1 2 3) and positions containing 1 for a vector (3 2 1). so the result should be x=(1 2 3 3 2 1 1 2 3 3 2 1).

Could somebody help me?

Thanks a lot

Answer 1

[KSSV]

 x=[-1 1 -1 1] ; 
 iwant = cell(1,length(x)) ; 
 for i = 1:length(x)
        if x(i) == -1
            iwant{i} = [1 2 3 ];
        elseif x(i) == 1
            iwant{i} = [3 2 1] ; 
        end
 end
 iwant = cell2mat(iwant) 

iwant = 1×12

1 2 3 3 2 1 1 2 3 3 2 1

 %% No loop
 % No loop
 x=[-1 1 -1 1] ;
 iwant = cell(1,length(x)) ;
 iwant(x==1) = {[3 2 1]} ; 
 iwant(x==-1) = {[1 2 3]} ; 
 iwant = cell2mat(iwant)

[Premysl Stastny]

Thank you!

Answer 2

[Matt J]

x=[-1 1 -1 1];

idx=(x==1);

X=nan(3,numel(x));

X(1,idx)=3; 
X(2,idx)=2; 
X(3,idx)=1;
X(:,~idx)=4-X(:,idx);

X=X(:).'

X = 1×12

1 2 3 3 2 1 1 2 3 3 2 1

Answer 3

[Matt J]

x=[-1 1 -1 1];

i=(x+3)/2;

V=[1 2 3;3 2 1].';

X=reshape( V(:,i) ,1,[])

X = 1×12

1 2 3 3 2 1 1 2 3 3 2 1

Answer 4

[Matt J]

x=[-1 1 -1 1];

x=strrep(10*x,10,[3,2,1]);

Warning: Inputs must be character vectors, cell arrays of character vectors, or string arrays.

x=strrep(x,-10,[1,2,3])

Warning: Inputs must be character vectors, cell arrays of character vectors, or string arrays.

x = 1×12

1 2 3 3 2 1 1 2 3 3 2 1

Answer 5

[Matt J]

x=[-1 1 -1 1];

X=kron(-x,[1,2,3]);
X=X+4*(X<0)

X = 1×12

1 2 3 3 2 1 1 2 3 3 2 1