Why does this if statement fail?

3 次查看（过去 30 天）
Renat Yakupov
Renat Yakupov 2020-9-7
评论： Stephen23 2020-9-7
I have noticed this strange behavior and I just can't figure why this is happening.
I have a script looping through a certain parameter and then saving some output results for certain values of that parameter. The relevant part of the script is:
for Thr=0.4:0.1:0.7
disp(Thr);
if Thr==0.5
disp('but I am here?');
end
if Thr==0.6
disp('am i here?');
end
end
>>
0.4000
0.5000
but I am here?
0.6000
0.7000
For some reason, it the if statement doesnt recognize Thr value of 0.6. If I use a step of 0.01, same happens for Thr values of 0.59, 0.58 and 0.57. I didnt test much further than that.
What is happening here?
  2 个评论
Renat Yakupov
Renat Yakupov 2020-9-7
I had no idea. That variable is different from 0.6 by 1e-16. That makes sense now. Thanks for the links!

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

KSSV
KSSV 2020-9-7
编辑：KSSV 2020-9-7
for Thr=0.4:0.1:0.7
disp(Thr);
if abs(Thr-0.5)<10^-3
disp('but I am here?');
end
if abs(Thr-0.6)<10^-3
disp('am i here?');
end
end
Read about comparing floating point numbers. It seems you are checking some options, you need not to do this. Please read abour debugging MATLAB files.
  2 个评论
Renat Yakupov
Renat Yakupov 2020-9-7
Thanks for the tip. In simpler cases like this, rounding to the first decimal also does the trick, but it certainly has to be more flexible for other cases.

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Logical 的更多信息

标签

产品


版本

R2018b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by