What is inf and nan

Question

Just a question that I m kind of confused about  So I was messing around with float  inf   and kind of wondering what it is used for   Also I noticed that if I add -inf   inf i get nan is that the same as Zero or not   I m confused about what the uses of these two values are   Also when I do nan - inf I don t get -inf I get nan I m sure it s all pretty simple but I stumbled upon them and didn t know what they do

User · Answer

Inf is infinity  it s a  bigger than all the other numbers  number  Try subtracting anything you want from it  it doesn t get any smaller  All numbers are  lt  Inf  -Inf is similar  but smaller than everything   NaN means not-a-number  If you try to do a computation that just doesn t make sense  you get NaN  Inf - Inf is one such computation  Usually NaN is used to just mean that some data is missing

User · Answer

I use inf -inf as initial values to find minimum maximum value of a measurement  Lets say that you measure temperature with a sensor and you want to keep track of minimum maximum temperature  The sensor might provide a valid temperature or might be broken  Pseudocode     initial value of the temperature t   float  nan               initial value of minimum temperature  so any measured temp  will be smaller t min   float  inf           initial value of maximum temperature  so any measured temp  will be bigger t max   float  -inf        while True        measure temperature  if sensor is broken t is not changed     t   measure              find new minimum temperature     t min   min t min  t         find new maximum temperature     t max   max t max  t     The above code works because inf -inf nan are valid for min max operation  so there is no need to deal with exceptions

User · Answer

nan means  not a number   a float value that you get if you perform a calculation whose result can t be expressed as a number  Any calculations you perform with NaN will also result in NaN   inf means infinity   For example    gt  gt  gt  2 float  inf   inf  gt  gt  gt  -2 float  inf   -inf  gt  gt  gt  float  inf  -float  inf   nan

User · Answer

You say       when i do nan - inf i dont get -inf i get nan   This is because any operation containing NaN as an operand would return NaN   A comparison with NaN would return an unordered result    gt  gt  gt  float  Inf      float  Inf   True  gt  gt  gt  float  NaN      float  NaN   False

User · Answer

inf is infinity - a value that is greater than any other value  -inf is therefore smaller than any other value   nan stands for Not A Number  and this is not equal to 0   Although positive and negative infinity can be said to be symmetric about 0  the same can be said for any value n  meaning that the result of adding the two yields nan  This idea is discussed in this math se question   Because nan is  literally  not a number  you can t do arithmetic with it  so the result of the second operation is also not a number  nan

[python] What is inf and nan?

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