Unrecognized function or variable 'e'

a = [1 2 3; 4 5 6; 7 8 9]
b = [7 5 6]
c = [19 23; 31 29; 17 13]
d = [e(1:2,:); f; e(3,:)];    % matrix f is inserted between the third and second row of e creating matrix d
e = [a(1,:);b(1,3);c(:,2).']  % matrix e consists of the first row of a, the second row of b and the transpose of the second column of c
f = c(:,1).'                  % matrix f is the transpose of the first column of matrix c  
m = diag(a(:))                %
m = [diag(a); diag(b)]        % 

I was wondering why the matrix e wasn't recognised as it was working before.

When I tried it with 3 zeros [a(1,:); 0 0 0;c(:,2).'] . Why won't it accept b as the middle row?

[DGM]

Maybe this is some help? I don't know what you're doing with the second row of b, but f and e need to be defined before you can use them.

a = [1 2 3; 4 5 6; 7 8 9]

a = 3×3

1 2 3 4 5 6 7 8 9

b = [7 5 6]

b = 1×3

7 5 6

c = [19 23; 31 29; 17 13]

c = 3×2

19 23 31 29 17 13

% "second row of b" ... but b only has one row?
% e = [a(1,:);b(2,:);c(:,2).']  % matrix e consists of the first row of a, the second row of b and the transpose of the second column of c
e = [a(1,:); b; c(:,2).'] % maybe you meant "the second row is b"?

e = 3×3

1 2 3 7 5 6 23 29 13

f = c(:,1).'                  % matrix f is the transpose of the first column of matrix c  

f = 1×3

19 31 17

% f and e need to exist first
d = [e(1:2,:); f; e(3,:)]    % matrix f is inserted between the third and second row of e creating matrix d

d = 4×3

1 2 3 7 5 6 19 31 17 23 29 13

Answer 1

[Image Analyst]

In your code:

a = [1 2 3; 4 5 6; 7 8 9]
b = [7 5 6]
c = [19 23; 31 29; 17 13]
d = [e(1:2,:); f; e(3,:)];    % matrix f is inserted between the third and second row of e creating matrix d
e = [a(1,:);b(1,3);c(:,2).']  % matrix e consists of the first row of a, the second row of b and the transpose of the second column of c
f = c(:,1).'                  % matrix f is the transpose of the first column of matrix c  
m = diag(a(:))                %
m = [diag(a); diag(b)]        % 

you can see that you're trying to create d by using e. The problem is e has not been created yet. You need to assign a 3-by-3 matrix to e BEFORE you try to use it while creating d.

You can't just swap those lines because you're creating e incorrectly. You have e as a 3 element row vector, a single number, then a 3 elemenet row vector in the bottom row. You can't have the second row be just a single number -- it must be 3 numbers in a row vector.

Then you're also trying to use f while creating d and you have the same problem. f has not yet been defined. You need to define f before you use it while creating d.

Not sure what you want for m but you have the first 3 rows as only a single column, then the bottom 3 rows have 3 columns. You can't have different number of columns when you're stitching arrays together vertically. So perhaps you want one of these two operations, which give different shapes

a = [1 2 3; 4 5 6; 7 8 9]
b = [7 5 6]
c = [19 23; 31 29; 17 13]
e = [a(1,:);b;c(:,2).']  % matrix e consists of the first row of a, the second row of b and the transpose of the second column of c
f = c(:,1).'                  % matrix f is the transpose of the first column of matrix c  
d = [e(1:2,:); f; e(3,:)];    % matrix f is inserted between the third and second row of e creating matrix d
m = diag(a(:))                %
m2 = [diag(a), diag(b)]        % 
m3 = [diag(a)'; diag(b)]        % 

m2 =

1 7 0 0

5 0 5 0

9 0 0 6

m3 =

1 5 9

7 0 0

0 5 0

0 0 6