You get a warning in each iteration:
Warning: Integer operands are required for colon operator when used as index
var1 = 0.1;
vec = 1:1000;
length_var = 1/(var1 * 0.1);
for ii=1:20
a = round(ii*(0.25*length_var));
b = a - 1 + 3*length_var;
fprintf('%.16g\n', b - a); % 298.9999999999999 in the first 8 iterations
c(ii,:) = vec(a:b);
end
In the 9th iteration b-a becomes 299. Then vec(a:b) has 300 elements, but c(ii,:) has 299 only.
Do not use floating point numbers as indices. You have applied a round for the index a already. Do this for b also. Or even better: Let length_var have an integer value:
fprintf('%.16g', 1/(var1 * 0.1))
99.99999999999999
This is an expected effect when working with floating point numbers stored with limited precision. To get more explanations search in this forum or in the net for "IEEE754".
