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.polw...@nhs.net> > Sent: Thursday, January 17, 2019 2:56 PM > To: PIKAL Petr <petr.pi...@precheza.cz>; Ben Tupper <btup...@bigelow.org> > Cc: r-help@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.pi...@precheza.cz] > Sent: 17 January 2019 13:53 > To: Ben Tupper; POLWART, Calum (COUNTY DURHAM AND DARLINGTON NHS > FOUNDATION TRUST) > Cc: r-help@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-boun...@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.polw...@nhs.net> > > Cc: r-help@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@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. 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