A bug? input: 1/0 output: -Inf
显示 更早的评论
if x=0, expected output of 1/x is Inf, but matlab output -Inf
load('x.mat')
x==0
1/0
1/x
2 个评论
Matt J
2024-2-13
Your attached file doesn't contain a variable called x.
Image Analyst
2024-2-13
x==0 is a comparison, not an assignment. Since you didn't assign x yet, you can't see if it's equal to zero, hence the error. I think you meant x=0, not x==0.
采纳的回答
"A bug? input: 1/0 output: -Inf"
Not a bug. Because your value x is actually negative zero not positive zero:
Lets try it now:
x = -0
1/x
num2hex(x) % yep, definitely negative zero
x = +0
1/x
num2hex(x) % yep, that is positive zero
So far everything is working exactly as expected. Note that a few simple arithmetic operations will convert negative zero to positive zero without affecting any other values, e.g. adding zero:
x = -0;
1/x
x = 0+x;
1/x
4 个评论
Lets take a look at your uploaded data:
S = load('x.mat');
x = S.deltaX
1/x
num2hex(x) % yep, definitely negative zero
qilin
2024-2-13
Dyuman Joshi
2024-2-13
How did you obtain that value?
Stephen23
2024-2-13
"maybe the next step is to figure out why my ''deltaX'' is negative zero"
Most likely it makes zero(!) difference: note that by definition negative and positive zeros have the same value, so if you are happy with your array being zero-value then simply multiply your array by one (or add zero) and move on to more important tasks.
更多回答（1 个）
Theorem: 1/0 = Inf if and only if 1/0 is also -Inf.
Proof: Assume first that 1/0=Inf and let us deduce the implication that 1/0=-Inf. By multiplying the numerator and denominator by -1, we obtain,
1/0 = (-1)/(-0) = (-1)/0 = -(1/0) = -Inf
proving the implication Now assume that 1/0=-Inf. Proceeding similarly,
1/0 = (-1)/(-0) = (-1)/0 = -(1/0) = -(-Inf) = +Inf
and the reverse implication is also proved. Q.E.D.
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