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PIKAL Petr

2019-Jan-17 13:52 UTC

[R] I can't get seq to behave how I think it should

Hi

Or you could use rounding.
which(round(lut, 3)==1.8)
[1] 401

Cheers
Petr
> -----Original Message-----
> From: R-help <r-help-bounces at r-project.org> On Behalf Of Ben
Tupper
> Sent: Thursday, January 17, 2019 2:43 PM
> To: POLWART, Calum (COUNTY DURHAM AND DARLINGTON NHS
> FOUNDATION TRUST) <calum.polwart at nhs.net>
> Cc: r-help at r-project.org
> Subject: Re: [R] I can't get seq to behave how I think it should
>
> Hi,
>
> This looks like a floating point reality bump - see
>
> https://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-
> these-numbers-are-equal_003f <https://cran.r-project.org/doc/FAQ/R-
> FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f>
>
> You can use other methods to finding your row - I would opt for
findInterval()
>
> > lut = seq(1.4, 2.1, by=0.001)
> > findInterval(1.8, lut)
> [1] 401
>
> findInterval() uses a rapid search to find the index in the look up table
(lut) that
> is just less than  or equal to the search value (in your example 1.8).
>
> Cheers,
> Ben
>
> > On Jan 17, 2019, at 8:33 AM, POLWART, Calum (COUNTY DURHAM AND
> DARLINGTON NHS FOUNDATION TRUST) via R-help <r-help at r-project.org>
> wrote:
> >
> > I am using seq with the expression seq(1.4, 2.1, by=0.001) to create a
> > sequence of references from 1.4 to 2.1 in 0.001 increments.  They
> > appear to be created correctly.  They have a related pair of data
> > which for the purposes of this we will call val.  I'm interested
in
> > the content on the row with seq = 1.8. But I can't seem to get it
> > returned.  I can get other values but not 1.8!  yet looking at row 401
> > there is nothing to indicate an issue
> >
> >> a = 1.4
> >> b = 2.1
> >> seq = seq(a, b, by=0.001)
> >> val = ceiling(seq * 50)
> >> s=data.frame(seq, val)
> >> s$val[seq==1.799]
> > [1] 90
> >> s$val[s$seq==1.8]
> > numeric(0)
> >> s$val[seq==1.8]
> > numeric(0)
> >> s$val[s$seq==1.800]
> > numeric(0)
> >> s$val[s$seq==1.801]
> > [1] 91
> >> head(s[s$seq>1.798,])
> >      seq val
> > 400 1.799  90
> > 401 1.800  90
> > 402 1.801  91
> > 403 1.802  91
> > 404 1.803  91
> > 405 1.804  91
> >
> >
> > Can anyone explain what's going on here and how I would correctly
find the
> content of row 401 by using an expression to equal the seq column?
> >
> >
> >
> >
> >
> >
> *******************************************************************
> ***
> > **********************************************
> >
> > This message may contain confidential information. If
> > ...{{dropped:25}}
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.Osobn? ?daje: Informace o zpracov?n? a ochran? osobn?ch ?daj? obchodn?ch
partner? PRECHEZA a.s. jsou zve?ejn?ny na:
https://www.precheza.cz/zasady-ochrany-osobnich-udaju/ | Information about
processing and protection of business partner?s personal data are available on
website: https://www.precheza.cz/en/personal-data-protection-principles/
D?v?rnost: Tento e-mail a jak?koliv k n?mu p?ipojen? dokumenty jsou d?v?rn? a
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POLWART, Calum (COUNTY DURHAM AND DARLINGTON NHS FOUNDATION TRUST)

2019-Jan-17 13:56 UTC

head link

[R] I can't get seq to behave how I think it should

Thanks guys.

I've used Petr's method and its working for me.

If the data had been from a calculation I'd have rounded it... just
didn't expect seq to break it!

C

-----Original Message-----
From: PIKAL Petr [mailto:petr.pikal at precheza.cz]
Sent: 17 January 2019 13:53
To: Ben Tupper; POLWART, Calum (COUNTY DURHAM AND DARLINGTON NHS FOUNDATION
TRUST)
Cc: r-help at r-project.org
Subject: RE: [R] I can't get seq to behave how I think it should

Hi

Or you could use rounding.
which(round(lut, 3)==1.8)
[1] 401

Cheers
Petr
> -----Original Message-----
> From: R-help <r-help-bounces at r-project.org> On Behalf Of Ben
Tupper
> Sent: Thursday, January 17, 2019 2:43 PM
> To: POLWART, Calum (COUNTY DURHAM AND DARLINGTON NHS FOUNDATION TRUST)
> <calum.polwart at nhs.net>
> Cc: r-help at r-project.org
> Subject: Re: [R] I can't get seq to behave how I think it should
>
> Hi,
>
> This looks like a floating point reality bump - see
>
> https://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-
> these-numbers-are-equal_003f <https://cran.r-project.org/doc/FAQ/R-
> FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f>
>
> You can use other methods to finding your row - I would opt for
> findInterval()
>
> > lut = seq(1.4, 2.1, by=0.001)
> > findInterval(1.8, lut)
> [1] 401
>
> findInterval() uses a rapid search to find the index in the look up
> table (lut) that is just less than  or equal to the search value (in your
example 1.8).
>
> Cheers,
> Ben
>
> > On Jan 17, 2019, at 8:33 AM, POLWART, Calum (COUNTY DURHAM AND
> DARLINGTON NHS FOUNDATION TRUST) via R-help <r-help at r-project.org>
> wrote:
> >
> > I am using seq with the expression seq(1.4, 2.1, by=0.001) to create
> > a sequence of references from 1.4 to 2.1 in 0.001 increments.  They
> > appear to be created correctly.  They have a related pair of data
> > which for the purposes of this we will call val.  I'm interested
in
> > the content on the row with seq = 1.8. But I can't seem to get it
> > returned.  I can get other values but not 1.8!  yet looking at row
> > 401 there is nothing to indicate an issue
> >
> >> a = 1.4
> >> b = 2.1
> >> seq = seq(a, b, by=0.001)
> >> val = ceiling(seq * 50)
> >> s=data.frame(seq, val)
> >> s$val[seq==1.799]
> > [1] 90
> >> s$val[s$seq==1.8]
> > numeric(0)
> >> s$val[seq==1.8]
> > numeric(0)
> >> s$val[s$seq==1.800]
> > numeric(0)
> >> s$val[s$seq==1.801]
> > [1] 91
> >> head(s[s$seq>1.798,])
> >      seq val
> > 400 1.799  90
> > 401 1.800  90
> > 402 1.801  91
> > 403 1.802  91
> > 404 1.803  91
> > 405 1.804  91
> >
> >
> > Can anyone explain what's going on here and how I would correctly
> > find the
> content of row 401 by using an expression to equal the seq column?
> >
> >
> >
> >
> >
> >
> *******************************************************************
> ***
> > **********************************************
> >
> > This message may contain confidential information. If
> > ...{{dropped:25}}
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.Osobn? ?daje: Informace o zpracov?n? a ochran? osobn?ch ?daj? obchodn?ch
partner? PRECHEZA a.s. jsou zve?ejn?ny na:
https://www.precheza.cz/zasady-ochrany-osobnich-udaju/ | Information about
processing and protection of business partner?s personal data are available on
website: https://www.precheza.cz/en/personal-data-protection-principles/
D?v?rnost: Tento e-mail a jak?koliv k n?mu p?ipojen? dokumenty jsou d?v?rn? a
podl?haj? tomuto pr?vn? z?vazn?mu prohl??en? o vylou?en? odpov?dnosti:
https://www.precheza.cz/01-dovetek/ | This email and any documents attached to
it may be confidential and are subject to the legally binding disclaimer:
https://www.precheza.cz/en/01-disclaimer/



********************************************************************************************************************

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PIKAL Petr

2019-Jan-17 14:30 UTC

head link

[R] I can't get seq to behave how I think it should

Hi

It is not seq problem, it is floating point numbers representation in finit
precision problem. Ben pointed to it and you could learn about it from FAQ 7.31.

Cheers
Petr
> -----Original Message-----
> From: POLWART, Calum (COUNTY DURHAM AND DARLINGTON NHS
> FOUNDATION TRUST) <calum.polwart at nhs.net>
> Sent: Thursday, January 17, 2019 2:56 PM
> To: PIKAL Petr <petr.pikal at precheza.cz>; Ben Tupper <btupper at
bigelow.org>
> Cc: r-help at r-project.org
> Subject: RE: [R] I can't get seq to behave how I think it should
>
> Thanks guys.
>
> I've used Petr's method and its working for me.
>
> If the data had been from a calculation I'd have rounded it... just
didn't expect
> seq to break it!
>
> C
>
> -----Original Message-----
> From: PIKAL Petr [mailto:petr.pikal at precheza.cz]
> Sent: 17 January 2019 13:53
> To: Ben Tupper; POLWART, Calum (COUNTY DURHAM AND DARLINGTON NHS
> FOUNDATION TRUST)
> Cc: r-help at r-project.org
> Subject: RE: [R] I can't get seq to behave how I think it should
>
> Hi
>
> Or you could use rounding.
> which(round(lut, 3)==1.8)
> [1] 401
>
> Cheers
> Petr
>
> > -----Original Message-----
> > From: R-help <r-help-bounces at r-project.org> On Behalf Of Ben
Tupper
> > Sent: Thursday, January 17, 2019 2:43 PM
> > To: POLWART, Calum (COUNTY DURHAM AND DARLINGTON NHS
> FOUNDATION TRUST)
> > <calum.polwart at nhs.net>
> > Cc: r-help at r-project.org
> > Subject: Re: [R] I can't get seq to behave how I think it should
> >
> > Hi,
> >
> > This looks like a floating point reality bump - see
> >
> > https://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-
> > these-numbers-are-equal_003f <https://cran.r-project.org/doc/FAQ/R-
> > FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f>
> >
> > You can use other methods to finding your row - I would opt for
> > findInterval()
> >
> > > lut = seq(1.4, 2.1, by=0.001)
> > > findInterval(1.8, lut)
> > [1] 401
> >
> > findInterval() uses a rapid search to find the index in the look up
> > table (lut) that is just less than  or equal to the search value (in
your example
> 1.8).
> >
> > Cheers,
> > Ben
> >
> > > On Jan 17, 2019, at 8:33 AM, POLWART, Calum (COUNTY DURHAM AND
> > DARLINGTON NHS FOUNDATION TRUST) via R-help <r-help at
r-project.org>
> > wrote:
> > >
> > > I am using seq with the expression seq(1.4, 2.1, by=0.001) to
create
> > > a sequence of references from 1.4 to 2.1 in 0.001 increments. 
They
> > > appear to be created correctly.  They have a related pair of data
> > > which for the purposes of this we will call val.  I'm
interested in
> > > the content on the row with seq = 1.8. But I can't seem to
get it
> > > returned.  I can get other values but not 1.8!  yet looking at
row
> > > 401 there is nothing to indicate an issue
> > >
> > >> a = 1.4
> > >> b = 2.1
> > >> seq = seq(a, b, by=0.001)
> > >> val = ceiling(seq * 50)
> > >> s=data.frame(seq, val)
> > >> s$val[seq==1.799]
> > > [1] 90
> > >> s$val[s$seq==1.8]
> > > numeric(0)
> > >> s$val[seq==1.8]
> > > numeric(0)
> > >> s$val[s$seq==1.800]
> > > numeric(0)
> > >> s$val[s$seq==1.801]
> > > [1] 91
> > >> head(s[s$seq>1.798,])
> > >      seq val
> > > 400 1.799  90
> > > 401 1.800  90
> > > 402 1.801  91
> > > 403 1.802  91
> > > 404 1.803  91
> > > 405 1.804  91
> > >
> > >
> > > Can anyone explain what's going on here and how I would
correctly
> > > find the
> > content of row 401 by using an expression to equal the seq column?
> > >
> > >
> > >
> > >
> > >
> > >
> >
> *******************************************************************
> > ***
> > > **********************************************
> > >
> > > This message may contain confidential information. If
> > > ...{{dropped:25}}
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> Osobn? ?daje: Informace o zpracov?n? a ochran? osobn?ch ?daj? obchodn?ch
> partner? PRECHEZA a.s. jsou zve?ejn?ny na: https://www.precheza.cz/zasady-
> ochrany-osobnich-udaju/ | Information about processing and protection of
> business partner?s personal data are available on website:
> https://www.precheza.cz/en/personal-data-protection-principles/
> D?v?rnost: Tento e-mail a jak?koliv k n?mu p?ipojen? dokumenty jsou d?v?rn?
> a podl?haj? tomuto pr?vn? z?vazn?mu prohl??en? o vylou?en? odpov?dnosti:
> https://www.precheza.cz/01-dovetek/ | This email and any documents
> attached to it may be confidential and are subject to the legally binding
> disclaimer: https://www.precheza.cz/en/01-disclaimer/
>
>
>
> *******************************************************************
> *************************************************
>
> This message may contain confidential information. If you are not the
intended
> recipient please inform the sender that you have received the message in
error
> before deleting it.
> Please do not disclose, copy or distribute information in this e-mail or
take any
> action in relation to its contents. To do so is strictly prohibited and may
be
> unlawful. Thank you for your co-operation.
>
> NHSmail is the secure email and directory service available for all NHS
staff in
> England and Scotland. NHSmail is approved for exchanging patient data and
> other sensitive information with NHSmail and other accredited email
services.
>
> For more information and to find out how you can switch,
> https://portal.nhs.net/help/joiningnhsmail
Osobn? ?daje: Informace o zpracov?n? a ochran? osobn?ch ?daj? obchodn?ch
partner? PRECHEZA a.s. jsou zve?ejn?ny na:
https://www.precheza.cz/zasady-ochrany-osobnich-udaju/ | Information about
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D?v?rnost: Tento e-mail a jak?koliv k n?mu p?ipojen? dokumenty jsou d?v?rn? a
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it may be confidential and are subject to the legally binding disclaimer:
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Martin Maechler

2019-Jan-18 15:47 UTC

head link

[R] I can't get seq to behave how I think it should

>>>>> PIKAL Petr 
>>>>>     on Thu, 17 Jan 2019 13:52:39 +0000 writes:
    > Hi
    > Or you could use rounding.

yes.

    > which(round(lut, 3)==1.8)
    > [1] 401

no!   This may work accidentally here, but in principle still
suffers for the same reasons as
the infamous FAQ 7.31 "Why doesn?t R think these numbers are equal?"
(link below) gives.

To be sure you should round to *integer*s (or other multiples of
2 ^{-k}, k \in {0,1,...,31}).

1.8 is not exactly representable as a (double precision)
floating point number in binary representation.
Your example here works because the rounding typically happens
to end up with the same binary repr ... this all relies on too
many details to be recommendable.

Martin Maechler
ETH Zurich and R Core team


    >> -----Original Message-----
    >> From: R-help <r-help-bounces at r-project.org> On Behalf Of
Ben Tupper
    >> Sent: Thursday, January 17, 2019 2:43 PM
    >> To: POLWART, Calum (COUNTY DURHAM AND DARLINGTON NHS
    >> FOUNDATION TRUST) <calum.polwart at nhs.net>
    >> Cc: r-help at r-project.org
    >> Subject: Re: [R] I can't get seq to behave how I think it
should
    >> 
    >> Hi,
    >> 
    >> This looks like a floating point reality bump - see
    >> 
    >>
https://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-
    >> these-numbers-are-equal_003f
<https://cran.r-project.org/doc/FAQ/R-
    >> FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f>
    >> 
    >> You can use other methods to finding your row - I would opt for
findInterval()
    >> 
    >> > lut = seq(1.4, 2.1, by=0.001)
    >> > findInterval(1.8, lut)
    >> [1] 401
    >> 
    >> findInterval() uses a rapid search to find the index in the look up
table (lut) that
    >> is just less than  or equal to the search value (in your example
1.8).
    >> 
    >> Cheers,
    >> Ben
    >> 
    >> > On Jan 17, 2019, at 8:33 AM, POLWART, Calum (COUNTY DURHAM AND
    >> DARLINGTON NHS FOUNDATION TRUST) via R-help <r-help at
r-project.org>
    >> wrote:
    >> >
    >> > I am using seq with the expression seq(1.4, 2.1, by=0.001) to
create a
    >> > sequence of references from 1.4 to 2.1 in 0.001 increments. 
They
    >> > appear to be created correctly.  They have a related pair of
data
    >> > which for the purposes of this we will call val.  I'm
interested in
    >> > the content on the row with seq = 1.8. But I can't seem to
get it
    >> > returned.  I can get other values but not 1.8!  yet looking at
row 401
    >> > there is nothing to indicate an issue
    >> >
    >> >> a = 1.4
    >> >> b = 2.1
    >> >> seq = seq(a, b, by=0.001)
    >> >> val = ceiling(seq * 50)
    >> >> s=data.frame(seq, val)
    >> >> s$val[seq==1.799]
    >> > [1] 90
    >> >> s$val[s$seq==1.8]
    >> > numeric(0)
    >> >> s$val[seq==1.8]
    >> > numeric(0)
    >> >> s$val[s$seq==1.800]
    >> > numeric(0)
    >> >> s$val[s$seq==1.801]
    >> > [1] 91
    >> >> head(s[s$seq>1.798,])
    >> >      seq val
    >> > 400 1.799  90
    >> > 401 1.800  90
    >> > 402 1.801  91
    >> > 403 1.802  91
    >> > 404 1.803  91
    >> > 405 1.804  91
    >> >
    >> >
    >> > Can anyone explain what's going on here and how I would
correctly find the
    >> content of row 401 by using an expression to equal the seq column?
    >> >
    >> >
    >> >
    >> >
    >> >
    >> >
    >> *******************************************************************
    >> ***
    >> > **********************************************
    >> >
    >> > This message may contain confidential information. If
    >> > ...{{dropped:25}}
    >> 
    >> ______________________________________________
    >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more,
see
    >> https://stat.ethz.ch/mailman/listinfo/r-help
    >> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
    >> and provide commented, minimal, self-contained, reproducible code.
    > Osobn? ?daje: Informace o zpracov?n? a ochran? osobn?ch ?daj?
obchodn?ch partner? PRECHEZA a.s. jsou zve?ejn?ny na:
https://www.precheza.cz/zasady-ochrany-osobnich-udaju/ | Information about
processing and protection of business partner?s personal data are available on
website: https://www.precheza.cz/en/personal-data-protection-principles/
    > D?v?rnost: Tento e-mail a jak?koliv k n?mu p?ipojen? dokumenty jsou
d?v?rn? a podl?haj? tomuto pr?vn? z?vazn?mu prohl??en? o vylou?en? odpov?dnosti:
https://www.precheza.cz/01-dovetek/ | This email and any documents attached to
it may be confidential and are subject to the legally binding disclaimer:
https://www.precheza.cz/en/01-disclaimer/

    > ______________________________________________
    > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
    > https://stat.ethz.ch/mailman/listinfo/r-help
    > PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
    > and provide commented, minimal, self-contained, reproducible code.

R help - Jan 2019 - I can't get seq to behave how I think it should

[R] I can't get seq to behave how I think it should

[R] I can't get seq to behave how I think it should

[R] I can't get seq to behave how I think it should

[R] I can't get seq to behave how I think it should