This thread, in addition to being a nice Thursday morning chuckle, should be de rigueur for 'R 101' users. It illustrates much of the thinking behind R in a very simple way, without taking itself too seriously. Well done all!
David Stevens **/**/ On 6/9/2021 8:35 AM, Bill Dunlap wrote: > Martin wrote > Use > num[num %% 2 == 1] > instead of much slower and ...@#^$ > num[ifelse(num %% 2 == 1, TRUE, FALSE)] > > Read the '[' as 'such that' when the subscript is logical > (=="Boolean"==TRUE/FALSE-values). > > [The original post had a typo/thinko, num<-num+i instead of num<-num+1, > which was simply an error, not a matter of style. R's vectorization makes > it easy to avoid such errors.] > > -Bill > > On Wed, Jun 9, 2021 at 2:56 AM Martin Maechler <[email protected]> > wrote: > >>>>>>> David Carlson on Sun, 6 Jun 2021 15:21:34 -0400 writes: >>> There is really no need for a loop: >>> num <- 1:100 >>> num[ifelse(num %% 2 == 1, TRUE, FALSE)] >>> [1] 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 >> 47 49 >>> [26] 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 >> 95 97 99 >> >> Well, and the above "works" but is really another proof of my >> year-long claim that people use ifelse(.) *MUCH MUCH* too often, >> and should really learn to use alternatives, in this case, >> "R 101" (*long* before fooverse): >> >> Use >> >> num[num %% 2 == 1] >> >> instead of much slower and ...@#^$ >> >> num[ifelse(num %% 2 == 1, TRUE, FALSE)] >> >> Martin Maechler >> ETH Zurich >> >>> On Sat, Jun 5, 2021 at 2:05 PM William Michels via R-help >>> <[email protected]> wrote: >> >> >> >> > i <- 1L; span <- 1:100; result <- NA; >> >> > for (i in span){ >> >> + ifelse(i %% 2 != 0, result[i] <- TRUE, result[i] <- FALSE) >> >> + } >> >> > span[result] >> >> [1] 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 >> 43 >> >> [............] >> >> ______________________________________________ >> [email protected] 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. >> > [[alternative HTML version deleted]] > > ______________________________________________ > [email protected] 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. > CAUTION: This email originated from outside of USU. If this appears to be a > USU employee, beware of impersonators. Do not click links, reply, download > images, or open attachments unless you verify the sender’s identity and know > the content is safe. > -- David K Stevens, PhD,PE Professor Civil and Environmental Engineering Utah State University Logan, UT 84322-8200 [email protected] 014357973229 [[alternative HTML version deleted]] ______________________________________________ [email protected] 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.
