Solved

# Matlab loop help

Posted on 2008-10-22
1,297 Views
Hey

i dont really understand whats happening in this example code i have. i dont understand matlabs implicit algebra. If you look at the attatched code can you please tell me how to write the bottom part of it with just "for loops" instead of the built in matlab algebra so i can better understand whats happening.

how do i write the:

x(i) = ( b(i) - A(i,i+1:n)*x(i+1:n) ) / A(i,i);

line of the loop:

for i = n-1:-1:1
x(i) = ( b(i) - A(i,i+1:n)*x(i+1:n) ) / A(i,i);
end

as a series of nested loops. when i it like this i think i'll be able to understand whats happening more easily and then hopefully i'll be able to play with the function!

thanks
``````function x = UpperTriangularSolve(A,b,n)

% function x = UpperTriangularSolve(A,b,n)

%

% Solve the system  A x = b  where A is assumed to be upper triangular,

% i.e. A(i,j) = 0 for j < i, and the diagonal is assumed to be nonzero,

% i.e. A(i,i) \= 0.

%

% ARGUMENTS:  A   upper triangular n x n matrix

%             b   right hand side column n-vector

%             n   integer matrix dimension

%

% RETURNS:    x   column n-vector solution

x = zeros(n,1);

x(n) = b(n)/A(n,n);

for i = n-1:-1:1

x(i) = ( b(i) - A(i,i+1:n)*x(i+1:n) ) / A(i,i);

end
``````
0
Question by:Ashwee
1 Comment

Accepted Solution

Ashwee earned 0 total points
ID: 22776012
erm i kind of worked it out :P

``````for i = n-1:-1:1

f = 0;

x(i) = b(i);

for m = i+1:n

m;

f = f + A(i,m)*x(m);

end

x(i) = x(i) - f;

x(i) = x(i) / A(i,i);

end
``````
0

## Featured Post

### Suggested Solutions

Bartender - Printing Duplicate Records On Label 2 168
dog bark java program 15 82
java constructor error 8 88
countHi challenge 25 84
How to remove superseded packages in windows w60 or w61 installation media (.wim) or online system to prevent unnecessary space. w60 means Windows Vista or Windows Server 2008. w61 means Windows 7 or Windows Server 2008 R2. There are various …
This article will show, step by step, how to integrate R code into a R Sweave document
This video teaches viewers about errors in exception handling.
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

#### Need Help in Real-Time?

Connect with top rated Experts

16 Experts available now in Live!