Insert data into the right index

I have two matrices:

A = [1   3   5   7   9;
     NaN NaN NaN NaN NaN];

B = [1 5 9;
     x y z];

The first row of each matrices is a some sort of 'index'

I'd like to move (or copy) [x y z] into the second row of matrices A with the same indices:

A = [1 3   5 7   9;
     x NaN y NaN z];

I'm happy if your solution / answer works well for larger matrices

[Jan]

What is the contents of B? You cannot mix doubles like 1 with characters like 'y' in an array, but you'd need a cell for this.

Answer 1

[Yao Li]

clear;
clc;
x=10;
y=20;
z=30;
A = [1   3   5   7   9;
     NaN NaN NaN NaN NaN];
B = [1 5 9;
     x y z];
 for i=1:length(A(1,:))
 for j=1:length(B(1,:))
if A(1,i)==B(1,j)
    A(2,i)=B(2,j);
else
end
 end
 end
 A

[Jeon]

Thanks. Uhm, but... Is there any method not using iterations?

[Yao Li]

try the function find, but I think you still need one for loop

[Jan]

Neither clear nor clc are useful here.

At least one loop can be removed easily:

 for iB = 1:length(B(1,:))
    A(2, A(1, :) == B(1, iB)) = B(2, iB);
 end

Does this work, when an element of B is not found? If not, use:

 for iB = 1:length(B(1,:))
    match = A(1, :) == B(1, iB);
    if any(match)
      A(2, match) = B(2, iB);
    end
 end

It is recommended to avoid "i" and "j" as variables, because they represent the sqrt(-1) also. In addition confusing "i" and "j" inside a loop is a famous programming error, which can be avoided by the more meaningful names "iA" and "iB".

Answer 2

[Andrei Bobrov]

for cell array

A = {1   3   5   7   9;
     NaN NaN NaN NaN NaN};
B = {1   5   9;
     'x' 'y' 'z'};

A(2,ismember([A{1,:}],[B{1,:}])) = B(2,:);

or

for double array

A = [1   3   5   7   9;
     NaN NaN NaN NaN NaN];
B = [1 5 9;
     100 500 900];

A(2,ismember(A(1,:),B(1,:))) = B(2,:);