| WHERE command returning -1 even if matching is there [message #93353] |
Wed, 22 June 2016 08:50  |
Sapna Mishra
Messages: 66
Registered: December 2015
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Member |
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Hello All,
I have a long float array say b_arr.
and I know it has a value 0.999254 at position 4556th in b_arr
but when I am doing:
i=where( b_arr EQ 0.999254)
print,i
-1
It should return i=4556. isn't??
How come is this possible any help please?
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| Re: WHERE command returning -1 even if matching is there [message #93355 is a reply to message #93354] |
Wed, 22 June 2016 09:14  |
Sapna Mishra
Messages: 66
Registered: December 2015
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Member |
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On Wednesday, June 22, 2016 at 9:32:13 PM UTC+5:30, Helder wrote:
> On Wednesday, June 22, 2016 at 4:50:22 PM UTC+1, Sapna Mishra wrote:
>> Hello All,
>>
>> I have a long float array say b_arr.
>> and I know it has a value 0.999254 at position 4556th in b_arr
>> but when I am doing:
>>
>> i=where( b_arr EQ 0.999254)
>> print,i
>> -1
>>
>> It should return i=4556. isn't??
>> How come is this possible any help please?
>
> Try printing:
> print, b_arr[4556]-0.999254
> print, b_arr[4556] eq 0.999254
>
> What do you get?
>
> Cheers,
> Helder
I am getting
3.57628e-07
0
I don't know what is wrong they both are the same numbers
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| Re: WHERE command returning -1 even if matching is there [message #93356 is a reply to message #93355] |
Wed, 22 June 2016 10:21 |
wlandsman
Messages: 743
Registered: June 2000
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Senior Member |
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Maybe the sky is falling
http://www.idlcoyote.com/math_tips/sky_is_falling.html
You might also use the following function for comparing floating point numbers
https://www.idlcoyote.com/programs/floats_equal.pro
On Wednesday, June 22, 2016 at 12:14:14 PM UTC-4, Sapna Mishra wrote:
> On Wednesday, June 22, 2016 at 9:32:13 PM UTC+5:30, Helder wrote:
>> On Wednesday, June 22, 2016 at 4:50:22 PM UTC+1, Sapna Mishra wrote:
>>> Hello All,
>>>
>>> I have a long float array say b_arr.
>>> and I know it has a value 0.999254 at position 4556th in b_arr
>>> but when I am doing:
>>>
>>> i=where( b_arr EQ 0.999254)
>>> print,i
>>> -1
>>>
>>> It should return i=4556. isn't??
>>> How come is this possible any help please?
>>
>> Try printing:
>> print, b_arr[4556]-0.999254
>> print, b_arr[4556] eq 0.999254
>>
>> What do you get?
>>
>> Cheers,
>> Helder
>
> I am getting
> 3.57628e-07
> 0
>
> I don't know what is wrong they both are the same numbers
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