求救，MATALB中NaN

heaventian

在matalb中， 下面程序：
a=nan
if a==nan, a=2; end
a

结果为什么a仍然是NaN呀？

[ 本帖最后由 ChaChing 于 2009-5-16 17:59 编辑 ]

eight

Because two NaNs are not equal to each other, logical operations involving NaNs always return false, except ~= (not equal). Consequently,
NaN ~= NaN
ans =
     1
NaN == NaN
ans =
     0

and the NaNs in a vector are treated as different unique elements.
unique([1 1 NaN NaN])
ans =
     1 NaN NaN

Use the isnan function to detect NaNs in an array.
isnan([1 1 NaN NaN])
ans =
     0     0     1     1

下次请先在matlab帮助中搜索一下

[ 本帖最后由 ChaChing 于 2009-5-16 18:02 编辑 ]

heaventian

谢谢，太懒了我