MATLAB: While loop iterating further than expected

MATLABprecisionwhile loop

Hi. I am experiencing a strange behavior in this simple script:
% CASE 1 - COMPUTES CORRECTLY
m1=1;
while m1<4.80
    m1=m1+0.1;
end
disp(m1);
% CASE 2 - DOES NOT COMPUTE CORRECTLY
m2=1;
while m2<4.90
    m2=m2+0.1;
end
disp(m2);
I obtain m1 = 4.8, as expected. However, I obtain m2 = 5.0, which implies the loop in CASE 2 has gone on for one iteration too many. Any idea why this might be happening? Is it a precision-related issue? I'm afraid I must be missing something very silly. Thank you for your help.

Best Answer

Rounding error. Try something like this:
m1=1;
while m1 < 4.80
    m1=round(m1+0.1, 2);  %To prevent m1 from drifting too far due to rounding error
end
disp(m1);
% CASE 2
m2=1;
while m2 < 4.90
    m2=round(m2+0.1, 2);
end
disp(m2);
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