one problem about rounding issue (but not the round function)

6 次查看（过去 30 天）
Lin Yang
Lin Yang 2018-7-10
编辑： Matt J 2018-7-10
Hi everyone, I encounter one problem in one part of my program. To simpilfy, it's:
A = 1.495:0.1:2.495;
for i = 1:11
disp(num2str(A(i),'%5.2f'));
end
it shows:
1.50
1.60
1.70
1.80
1.90
2.00
2.10
2.20
→2.29
2.40
2.50
In a different machine it shows:
1.50
1.60
1.70
1.80
1.90
2.00
2.10
2.20
2.30
2.40
→2.49
This may be due to "the round function rounds away from zero to the integer with larger magnitude" in this link's sentence： https://ww2.mathworks.cn/help/matlab/ref/round.html?lang=en But I'm not sure. could anyone help me solve this problem, to let the program stably display correct rounding result? Many thanks.

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采纳的回答

Matt J
Matt J 2018-7-10
编辑：Matt J 2018-7-10
Because of floating point errors, the "2.2950" is really 2.294999999999999999999999999999999999999, which rounds to 2.29. Do instead
A = round( 1.495:0.1:2.495 ,2);
or
disp(num2str(round( A(i) ,2) ,'%5.2f'))

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