How to make a loop to add 3 elemts in matrix of zeros(n,n)?

n= input('enter the value of n:-->');
A= zeroes(n,n); %n must be greater than 3

i want to add [1 4 1] in second row after skipping first 0 if n=4

and if n=5 add [1 4 1] in second row after skipping first 0 and add [ 1 4 1] to third row after skip two 0`s.

for example:

A = [0 0 0;
     0 0 0;
     0 0 0]

if n=3

add [ 1 4 1] to 2nd row

then

A = [ 0 0 0;
      1 4 1;
      0 0 0]

if n=4

A = [0 0 0 0;
     0 1 4 1;
     0 0 0 0]

if n=5

A = [ 0 0 0 0 0;
      1 4 1 0 0;
      0 1 4 1 0;
      0 0 1 4 1;
      0 0 0 0 0];

similarly ahead

help me

Answer 1

[Mikhail]

As i understand, u need this:

n= input('enter the value of n:-->');

A= zeroes(n,n); %n must be greater than 3

for i=2:n-1 % loop from 2nd to (n-1) row

 A(i,:)=[zeros(1,i-2),[1 4 1],zeros(1,n-i-1)] %explicit structure of row i
end

[Mikhail]

So, your row with number i (from 2 to n-1) consist of: (i-2) zeros, then array [1 4 1], then again zeros.

[Avtar Singh]

yes, but above does not work

[the cyclist]

Use zeros() instead of zeroes().

[Avtar Singh]

yes i do but it gives Expression or statement is incomplete or incorrect.

[the cyclist]

Does this work for you?

n = 5;

A= zeros(n,n); %n must be greater than 3

for i=2:n-1 % loop from 2nd to (n-1) row
 A(i,:) = [zeros(1,i-2),[1 4 1],zeros(1,n-i-1)] %explicit structure of row i
end

[Avtar Singh]

yes bro thanks very much

[Avtar Singh]

further with that one if i want to make first row as 1 0 0 ..... and last row as ........... 0 0 0 1 then what can i do???

[Mikhail]

write after this:

A(1,:)=[1, zeros(1,n-1)] % 1st row=[1 0 0 0 0 ...]

A(n,:)=[zeros(1,n-1), 1] % nth row =[0 0 0 ... 0 0 1]

[Avtar Singh]

thanks bro

[Avtar Singh]

clear all

a=[1,1,0;4,4,1;7,5,1;15,2,1;6,4,3]

n = input('enter the number of passing points of curve:--->>')

A= zeros(n,n); %n must be greater than 3

for i=2:n-1 % loop from 2nd to (n-1) row

 A(i,:) = [zeros(1,i-2),[1 4 1],zeros(1,n-i-1)]; %explicit structure of 
row i

end

A(1,1)=1;

A(n,n)=1;

R=[0 0 0; 3*(a(3,:)-a(1,:)); 3*(a(4,:)-a(2,:));3*(a(5,:)-a(3,:));0 0 0];

X=inv(A)

T=X*R;

u=[0:0.01:1]'

U=[u.^3 u.^u u u.^0];

M=[2 -2 1 1;-3 3 -2 -1 ;0 0 1 0;1 0 0 0];

B=[0 0 0;a(1,:);0 0 0;T(2,:)];

P=U*M*B;

plot3(P(:,1),P(:,2),P(:,3));

hold on

B1=[a(1,:);a(2,:);T(2,:);T(3,:)];

P1=U*M*B1;

plot3(P1(:,1),P1(:,2),P1(:,3));

I want to join these curves by smooth one but i cant help me