Weighting based on Eigenvector method

i am constructing a simple eigenvector method for a 6 rows X 10 columns matrix.This is main part of the code, the values in PM=[] have been omitted due to the large amount of input numbers

PM=[]
Wt(:,1)=[1;0;0;0;0;0;0;0;0;0];
[len,width]=size(PM);
delta(:,1)=[1 1 1 1 1 1 1 1 1 1]';
trial=18;
for t=2:trial
  Wt1(:,t)=PM*Wt(:,t-1);
  max_eig=sum(Wt1(:,t));
  Wtnorm1(:,t)=Wt1(:,t)./max_eig;
  delta(:,t)=abs(Wt(:,t-1)-Wtnorm1(:,t));
  if delta(:,t-1)>=1e-6
      Wt(:,t)=Wtnorm1(:,t);
  else
      CI=(max_eig-width)/(width-1);
      weight=Wtnorm1;
      break
  end
end
final_weight=weight(:,length(weight));

unfortunately i cant seem to diagnose this error:

??? Attempted to access weight(:,10); index out of bounds because size(weight)=[10,4].

Error in ==> eigenvector at 31 final_weight=weight(:,length(weight));

i am pretty new to matlab so i am not sure how to read these error messages.thanks alot!

[the cyclist]

Are you able to give a toy example of PM that will exhibit the error behavior, without all the real values? I tried PM = rand(6,10), but that gives an error earlier in the code.

Answer 1

[the cyclist]

It is hard to dig deeper without being able to run your code. However, the specific error is that length(weight) is equal to 10 (because length() returns the longer dimension of a 2-d array). But since weight is 10x4, you are trying to access the 10th column of an array that only has 4 columns. Hence, the error.

Answer 2

[Richard]

hi thanks alot for assisting me on this,pretty much stuck at this stage for at least a week.This is the original code(3x3) which i am basing my weighting method upon:

PM = [1/1 2/1 39/10;1/2 1/1 2/1;10/39 1/2 1/1]
Wt(:,1)=[1;0;0]
[len,width]=size(PM);
delta(:,1)=[1 1 1]';
trial=18;
for t=2:trial
  Wt1(:,t)=PM*Wt(:,t-1);
  max_eig=sum(Wt1(:,t));
  Wtnorm1(:,t)=Wt1(:,t)./max_eig;
  delta(:,t)=abs(Wt(:,t-1)-Wtnorm1(:,t));
  if delta(:,t-1)>=1e-6
      Wt(:,t)=Wtnorm1(:,t);
  else
      CI=(max_eig-width)/(width-1);
      weight=Wtnorm1;
      break
  end
end
final_weight=weight(:,length(weight));
disp(['After',num2str(t),'iterations.....'])
disp(['The pairwise comparison result is [',num2str(final_weight(1)),' ',num2str(final_weight(2)),'',num2str(final_weight(3)),']'])

then for my 6x10 matrix the actual values are:

PM=[14.3/14.3 14.3/10 14.3/18 14.3/2.1 14.3/558 14.3/16.66 14.3/3.33 14.3/0.7 14.3/5 14.3/0.25;
  10/14.3 10/10 10/18 10/2.1 10/558 10/16.66 10/3.33 10/0.7 10/5 10/0.25;
  18/14.3 18/10 18/18 18/2.1 18/558 18/16.66 18/3.33 18/0.7 18/5 18/0.25;
  2.1/14.3 2.1/10 2.1/18 2.1/2.1 2.1/558 2.1/16.66 2.1/3.33 2.1/0.7 2.1/5 2.1/0.25;
  558/14.3 558/10 558/18 558/2.1 558/558 558/16.66 558/3.33 558/0.7 558/5 558/0.25;
  16.66/14.3 16.66/10 16.66/18 16.66/2.1 16.66/558 16.66/16.66 16.66/3.33 16.66/0.7 16.66/5 16.66/0.25;
  3.33/14.3 3.33/10 3.33/18 3.33/2.1 3.33/558 3.33/16.66 3.33/3.33 3.33/0.7 3.33/5 3.33/0.25;
  0.7/14.3 0.7/10 0.7/18 0.7/2.1 0.7/558 0.7/16.66 0.7/3.33 0.7/0.7 0.7/5 0.7/0.25;
  5/14.3 5/10 5/18 5/2.1 5/558 5/16.66 5/3.33 5/0.7 5/5 5/0.25;
  0.25/14.3 0.25/10 0.25/18 0.25/2.1 0.25/558 0.25/16.66 0.25/3.33 0.25/0.7 0.25/5 0.25/0.25]

[the cyclist]

I won't say that I deeply understand code. But, working backward, what is happening is the following:

(1) The 2nd dimension of "weight" is not as long as length(weight), so you are trying to index into an element that does not exist. In other words, the variable "weight" doesn't have enough columns.

(2) The reason that "weight" doesn't have enough columns is that you break out of the loop before you have created the columns you need.

(3) You break out of the loop based on the value of delta.

So, I am not exactly sure what is going wrong, but something in that chain is not working in the same way as your smaller 3x3 example.