# Index exceeds matrix dimensions

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Ken on 14 Oct 2016
Commented: Walter Roberson on 15 Oct 2016
I have the foll. program and when I run it, I get the above error msg i.e. 'Index exceeds matrix dimensions'. Not sure what causes this msg. Please help.
A=[2,2,3,4,5;2,3,6,8,9;3,4,7,6,4;2,9,0,4,5;3,8,7,9,2];
%x=1;
%y=1;
OptimalPath=[2,2];
CurrentPos=[2,2];
min=99;
for x=OptimalPath(end,1)-1:OptimalPath(end,1)+1;
for y= OptimalPath(end,2)-1:OptimalPath(end,2)+1
if A(x,y)<min
min=A(x,y);
end
CurrentPos(1)=CurrentPos(1)+x;
CurrentPos(2)=CurrentPos(2)+y;
OptimalPath=[OptimalPath;CurrentPos]
end
end

Roche de Guzman on 14 Oct 2016
Your y For Loop counter is becoming greater than 5 (the number of columns of your matrix A). Since you are using y for indexing, A(x,y), then you are exceeding the matrix dimensions.
Walter Roberson on 15 Oct 2016
dbstop if error
then run your code. When it stops, examine the size() of each variable being indexed, and examine the value of each of the indexing expressions. The more difficult part is then trying to figure out either how the indexing expression got to be that wrong value, or trying to figure out why the variable being indexed is not as large as expected.
(Hint for the future: if the variable being indexed is not as large as expected, check to see if you are using the / operator somewhere that you need the ./ operator.)