MATLAB: Matrix in a matrix…………..

arrayindexing

In matlab:

x =

     1     3     6
     8     3     6
     1     9     0

y =

     5     4     6
     7     9     4
     2     6     4

Z=x(y)

Z =

     3     3     9
     6     0     3
     8     9     3

How can i find Z manually……….

Best Answer

x is an array with 9 elements. y is a matrix of indices each in the range 1 to 9.

y(1) is 5, so the first output of x(y) is x(y(1)) which is x(5), the fifth element of x. Array elements are numbered down columns

1 4 7
2 5 8
3 6 9

Related Solutions

MATLAB: Exercise: Add 3 to just the odd elements of x=[2 5 1 6]

Create z = x and then modify the elements of z directly using the indexes contained in y. E.g.,

z = x;
z(y) = z(y) + 3;

MATLAB: How to find and remove the nonzero duplicates in each column of a matrix

Given

"matrix of integers"
"the first row is always the column number"
"the duplicate, if exists, is always the same integer as the column number"

Try this

X = [ 1 2 3 4 5
      2 9 5 3 8
      7 5 4 0 1
      6 7 3 2 0
      3 1 6 7 9 ];
Y = nan( size(X) );
for jj = 1 : size( X, 2)
    isdub = X( :, jj ) == jj;
    if  any( isdub(2:end) ) 
        col = X(:,jj);
        col( isdub ) = [];
        Y(:,jj) = cat( 1, col, zeros(sum(isdub),1) );
    else
        Y(:,jj) = X(:,jj);
    end
end

result

>> Y
Y =
     1     2     5     4     5
     2     9     4     3     8
     7     5     6     0     1
     6     7     0     2     0
     3     1     0     7     9
>>

This code trades performance for readability.

&nbsp

Requirement of comment: "modify the codes ... keep the one in the first row and only remove the other one"

Y = nan( size(X) );
for jj = 1 : size( X, 2)
    col = X(2:end,jj);
    isdub = col == jj;
    if  any( isdub ) 
        col( isdub ) = [];
        Y(:,jj) = cat( 1, jj, col, zeros(sum(isdub),1) );
    else
        Y(:,jj) = X(:,jj);
    end
end

result

>> Y
Y =
     1     2     3     4     5
     2     9     5     3     8
     7     5     4     0     1
     6     7     6     2     0
     3     1     0     7     9

Best Answer

Related Solutions

MATLAB: Exercise: Add 3 to just the odd elements of x=[2 5 1 6]

MATLAB: How to find and remove the nonzero duplicates in each column of a matrix

Related Question