# [R] Matching/checking for occurence when values are double?

Sat Sep 10 21:02:43 CEST 2016

```Actually, there was another reason for the function equal() but I
wasn't remembering what.
all.equal doesn't recycle its arguments, just see this example.

equal <- function(x, y, eps = .Machine\$double.eps^0.5) abs(x - y) < eps

x <- seq(0, 1, by = 0.2)
x == 0.6
all.equal(x, 0.6)
equal(x, 0.6)

> Not exactly, all.equal is much more complete.
> It accepts all kinds of objects, not just vectors.
>
>
>
>
> Citando Ivan Calandra <ivan.calandra at univ-reims.fr>:
>
>> Hi,
>>
>> Not sure, but it seems that your function equal() is exactly what
>> all.equal() does, isn't it?
>>
>> Ivan
>>
>> --
>> Ivan Calandra, PhD
>> Scientific Mediator
>> University of Reims Champagne-Ardenne
>> GEGENAA - EA 3795
>> CREA - 2 esplanade Roland Garros
>> 51100 Reims, France
>> +33(0)3 26 77 36 89
>> ivan.calandra at univ-reims.fr
>> --
>> https://www.researchgate.net/profile/Ivan_Calandra
>> https://publons.com/author/705639/
>>
>> Le 09/09/2016 à 14:47, ruipbarradas at sapo.pt a écrit :
>>> Hello,
>>>
>>> See FAQ 7.31.
>>> It's irrelevant if you write 100 or 100.0, the values are the
>>> same. The difference would be between 100 (double) and 100L
>>> (integer).
>>> To check for equality between floating-point numbers you can use,
>>> for instance, the following function.
>>>
>>> equal <- function(x, y, eps = .Machine\$double.eps^0.5) abs(x - y) < eps
>>>
>>> equal(100, 100 + 2e-15)
>>> [1] TRUE
>>>
>>> Hope this helps,
>>>
>>>
>>>
>>>
>>> Citando Matti Viljamaa <mviljamaa at kapsi.fi>:
>>>
>>>> I need to pick from a dataset those rows that have a double value
>>>> set to 100.
>>>> However since the values in this column are like the following:
>>>>
>>>> [1] 121.11750  89.36188 115.44320  99.44964  92.74571 107.90180
>>>> [7] 138.89310 125.14510  81.61953  95.07307  88.57700  94.85971
>>>> [13]  88.96280 114.11430 100.53410 120.41910 114.42690
>>>> …
>>>>
>>>> Then can I match against 100 or 100.0? Or do I need to match
>>>> against 100.00000 or something else?
>>>>
>>>> E.g. does
>>>>
>>>> 100.0 %in% kidmomiq\$mom_iq
>>>>
>>>> produce a truthful match result with this kind of data (I’m
>>>> getting 0 occurrences, which might be correct, but I’m not sure)?
>>>> ______________________________________________
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>>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>> ______________________________________________
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>>> and provide commented, minimal, self-contained, reproducible code.
>>
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