Hello,
Maybe I am not understanding how negative indexing works but 1) This is right. (1:10)[-1] #[1] 2 3 4 5 6 7 8 9 10 2) Are these right? They are at least surprising to me. (1:10)[-0] #integer(0) (1:10)[-seq_len(0)] #integer(0) It was the last example that made me ask, seq_len(0) whould avoid an if/else or something similar. Thanks in advance, Rui Barradas ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
El sáb., 4 ago. 2018 a las 15:32, Rui Barradas
(<[hidden email]>) escribió: > > Hello, > > Maybe I am not understanding how negative indexing works but > > 1) This is right. > > (1:10)[-1] > #[1] 2 3 4 5 6 7 8 9 10 > > 2) Are these right? They are at least surprising to me. > > (1:10)[-0] > #integer(0) > > (1:10)[-seq_len(0)] > #integer(0) > > > It was the last example that made me ask, seq_len(0) whould avoid an > if/else or something similar. I think it's ok, because there is no negative zero integer, so -0 is 0. 1.0/-0L # Inf 1.0/-0.0 # - Inf And the same can be said for integer(0), which is the result of seq_len(0): there is no negative empty integer. Iñaki > > > Thanks in advance, > > Rui Barradas > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
Às 15:51 de 04/08/2018, Iñaki Úcar escreveu: > El sáb., 4 ago. 2018 a las 15:32, Rui Barradas > (<[hidden email]>) escribió: >> >> Hello, >> >> Maybe I am not understanding how negative indexing works but >> >> 1) This is right. >> >> (1:10)[-1] >> #[1] 2 3 4 5 6 7 8 9 10 >> >> 2) Are these right? They are at least surprising to me. >> >> (1:10)[-0] >> #integer(0) >> >> (1:10)[-seq_len(0)] >> #integer(0) >> >> >> It was the last example that made me ask, seq_len(0) whould avoid an >> if/else or something similar. > > I think it's ok, because there is no negative zero integer, so -0 is 0. Ok, this makes sense, I should have thought about that. > > 1.0/-0L # Inf > 1.0/-0.0 # - Inf > > And the same can be said for integer(0), which is the result of > seq_len(0): there is no negative empty integer. I'm not completely convinced about this one, though. I would expect -seq_len(n) to remove the first n elements from the vector, therefore, when n == 0, it would remove none. And integer(0) is not the same as 0. (1:10)[-0] == (1:10)[0] == integer(0) # empty (1:10)[-seq_len(0)] == (1:10)[-integer(0)] And I have just reminded myself to run identical(-integer(0), integer(0)) It returns TRUE so my intuition is wrong, R is right. End of story. Thanks for the help, Rui Barradas > > Iñaki > >> >> >> Thanks in advance, >> >> Rui Barradas >> >> ______________________________________________ >> [hidden email] mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
This should more clearly illustrate the issue:
c(1, 2, 3, 4)[-seq_len(4)] #> numeric(0) c(1, 2, 3, 4)[-seq_len(3)] #> [1] 4 c(1, 2, 3, 4)[-seq_len(2)] #> [1] 3 4 c(1, 2, 3, 4)[-seq_len(1)] #> [1] 2 3 4 c(1, 2, 3, 4)[-seq_len(0)] #> numeric(0) Created on 2018-08-05 by the reprex package (v0.2.0.9000). On Sun, Aug 5, 2018 at 3:58 AM Rui Barradas <[hidden email]> wrote: > > > Às 15:51 de 04/08/2018, Iñaki Úcar escreveu: > > El sáb., 4 ago. 2018 a las 15:32, Rui Barradas > > (<[hidden email]>) escribió: > >> > >> Hello, > >> > >> Maybe I am not understanding how negative indexing works but > >> > >> 1) This is right. > >> > >> (1:10)[-1] > >> #[1] 2 3 4 5 6 7 8 9 10 > >> > >> 2) Are these right? They are at least surprising to me. > >> > >> (1:10)[-0] > >> #integer(0) > >> > >> (1:10)[-seq_len(0)] > >> #integer(0) > >> > >> > >> It was the last example that made me ask, seq_len(0) whould avoid an > >> if/else or something similar. > > > > I think it's ok, because there is no negative zero integer, so -0 is 0. > > Ok, this makes sense, I should have thought about that. > > > > > 1.0/-0L # Inf > > 1.0/-0.0 # - Inf > > > > And the same can be said for integer(0), which is the result of > > seq_len(0): there is no negative empty integer. > > I'm not completely convinced about this one, though. > I would expect -seq_len(n) to remove the first n elements from the > vector, therefore, when n == 0, it would remove none. > > And integer(0) is not the same as 0. > > (1:10)[-0] == (1:10)[0] == integer(0) # empty > > (1:10)[-seq_len(0)] == (1:10)[-integer(0)] > > > And I have just reminded myself to run > > identical(-integer(0), integer(0)) > > It returns TRUE so my intuition is wrong, R is right. > End of story. > > Thanks for the help, > > Rui Barradas > > > > > Iñaki > > > >> > >> > >> Thanks in advance, > >> > >> Rui Barradas > >> > >> ______________________________________________ > >> [hidden email] mailing list > >> https://stat.ethz.ch/mailman/listinfo/r-devel > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
Thanks.
This is exactly the doubt I had. Rui Barradas Às 05:26 de 05/08/2018, Kenny Bell escreveu: > This should more clearly illustrate the issue: > > c(1, 2, 3, 4)[-seq_len(4)] > #> numeric(0) > c(1, 2, 3, 4)[-seq_len(3)] > #> [1] 4 > c(1, 2, 3, 4)[-seq_len(2)] > #> [1] 3 4 > c(1, 2, 3, 4)[-seq_len(1)] > #> [1] 2 3 4 > c(1, 2, 3, 4)[-seq_len(0)] > #> numeric(0) > Created on 2018-08-05 by the reprex package (v0.2.0.9000). > > On Sun, Aug 5, 2018 at 3:58 AM Rui Barradas <[hidden email] > <mailto:[hidden email]>> wrote: > > > > Às 15:51 de 04/08/2018, Iñaki Úcar escreveu: > > El sáb., 4 ago. 2018 a las 15:32, Rui Barradas > > (<[hidden email] <mailto:[hidden email]>>) escribió: > >> > >> Hello, > >> > >> Maybe I am not understanding how negative indexing works but > >> > >> 1) This is right. > >> > >> (1:10)[-1] > >> #[1] 2 3 4 5 6 7 8 9 10 > >> > >> 2) Are these right? They are at least surprising to me. > >> > >> (1:10)[-0] > >> #integer(0) > >> > >> (1:10)[-seq_len(0)] > >> #integer(0) > >> > >> > >> It was the last example that made me ask, seq_len(0) whould avoid an > >> if/else or something similar. > > > > I think it's ok, because there is no negative zero integer, so -0 > is 0. > > Ok, this makes sense, I should have thought about that. > > > > > 1.0/-0L # Inf > > 1.0/-0.0 # - Inf > > > > And the same can be said for integer(0), which is the result of > > seq_len(0): there is no negative empty integer. > > I'm not completely convinced about this one, though. > I would expect -seq_len(n) to remove the first n elements from the > vector, therefore, when n == 0, it would remove none. > > And integer(0) is not the same as 0. > > (1:10)[-0] == (1:10)[0] == integer(0) # empty > > (1:10)[-seq_len(0)] == (1:10)[-integer(0)] > > > And I have just reminded myself to run > > identical(-integer(0), integer(0)) > > It returns TRUE so my intuition is wrong, R is right. > End of story. > > Thanks for the help, > > Rui Barradas > > > > > Iñaki > > > >> > >> > >> Thanks in advance, > >> > >> Rui Barradas > >> > >> ______________________________________________ > >> [hidden email] <mailto:[hidden email]> mailing list > >> https://stat.ethz.ch/mailman/listinfo/r-devel > > ______________________________________________ > [hidden email] <mailto:[hidden email]> mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
This is Circle 8..1.13 of the R Inferno.
On 05/08/2018 06:57, Rui Barradas wrote: > Thanks. > This is exactly the doubt I had. > > Rui Barradas > > Às 05:26 de 05/08/2018, Kenny Bell escreveu: >> This should more clearly illustrate the issue: >> >> c(1, 2, 3, 4)[-seq_len(4)] >> #> numeric(0) >> c(1, 2, 3, 4)[-seq_len(3)] >> #> [1] 4 >> c(1, 2, 3, 4)[-seq_len(2)] >> #> [1] 3 4 >> c(1, 2, 3, 4)[-seq_len(1)] >> #> [1] 2 3 4 >> c(1, 2, 3, 4)[-seq_len(0)] >> #> numeric(0) >> Created on 2018-08-05 by the reprex package (v0.2.0.9000). >> >> On Sun, Aug 5, 2018 at 3:58 AM Rui Barradas <[hidden email] >> <mailto:[hidden email]>> wrote: >> >> >> >> Às 15:51 de 04/08/2018, Iñaki Úcar escreveu: >> > El sáb., 4 ago. 2018 a las 15:32, Rui Barradas >> > (<[hidden email] <mailto:[hidden email]>>) escribió: >> >> >> >> Hello, >> >> >> >> Maybe I am not understanding how negative indexing works but >> >> >> >> 1) This is right. >> >> >> >> (1:10)[-1] >> >> #[1] 2 3 4 5 6 7 8 9 10 >> >> >> >> 2) Are these right? They are at least surprising to me. >> >> >> >> (1:10)[-0] >> >> #integer(0) >> >> >> >> (1:10)[-seq_len(0)] >> >> #integer(0) >> >> >> >> >> >> It was the last example that made me ask, seq_len(0) whould >> avoid an >> >> if/else or something similar. >> > >> > I think it's ok, because there is no negative zero integer, so -0 >> is 0. >> >> Ok, this makes sense, I should have thought about that. >> >> > >> > 1.0/-0L # Inf >> > 1.0/-0.0 # - Inf >> > >> > And the same can be said for integer(0), which is the result of >> > seq_len(0): there is no negative empty integer. >> >> I'm not completely convinced about this one, though. >> I would expect -seq_len(n) to remove the first n elements from the >> vector, therefore, when n == 0, it would remove none. >> >> And integer(0) is not the same as 0. >> >> (1:10)[-0] == (1:10)[0] == integer(0) # empty >> >> (1:10)[-seq_len(0)] == (1:10)[-integer(0)] >> >> >> And I have just reminded myself to run >> >> identical(-integer(0), integer(0)) >> >> It returns TRUE so my intuition is wrong, R is right. >> End of story. >> >> Thanks for the help, >> >> Rui Barradas >> >> > >> > Iñaki >> > >> >> >> >> >> >> Thanks in advance, >> >> >> >> Rui Barradas >> >> >> >> ______________________________________________ >> >> [hidden email] <mailto:[hidden email]> mailing list >> >> https://stat.ethz.ch/mailman/listinfo/r-devel >> >> ______________________________________________ >> [hidden email] <mailto:[hidden email]> mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel >> > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > -- Patrick Burns [hidden email] twitter: @burnsstat @portfolioprobe http://www.portfolioprobe.com/blog http://www.burns-stat.com (home of: 'Impatient R' 'The R Inferno' 'Tao Te Programming') ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
Thanks,
This is what I needed. I had read the R Inferno a long time ago and apparently forgot this one. Rui Barradas Às 08:46 de 05/08/2018, Patrick Burns escreveu: > This is Circle 8..1.13 of the R Inferno. > > > On 05/08/2018 06:57, Rui Barradas wrote: >> Thanks. >> This is exactly the doubt I had. >> >> Rui Barradas >> >> Às 05:26 de 05/08/2018, Kenny Bell escreveu: >>> This should more clearly illustrate the issue: >>> >>> c(1, 2, 3, 4)[-seq_len(4)] >>> #> numeric(0) >>> c(1, 2, 3, 4)[-seq_len(3)] >>> #> [1] 4 >>> c(1, 2, 3, 4)[-seq_len(2)] >>> #> [1] 3 4 >>> c(1, 2, 3, 4)[-seq_len(1)] >>> #> [1] 2 3 4 >>> c(1, 2, 3, 4)[-seq_len(0)] >>> #> numeric(0) >>> Created on 2018-08-05 by the reprex package (v0.2.0.9000). >>> >>> On Sun, Aug 5, 2018 at 3:58 AM Rui Barradas <[hidden email] >>> <mailto:[hidden email]>> wrote: >>> >>> >>> >>> Às 15:51 de 04/08/2018, Iñaki Úcar escreveu: >>> > El sáb., 4 ago. 2018 a las 15:32, Rui Barradas >>> > (<[hidden email] <mailto:[hidden email]>>) escribió: >>> >> >>> >> Hello, >>> >> >>> >> Maybe I am not understanding how negative indexing works but >>> >> >>> >> 1) This is right. >>> >> >>> >> (1:10)[-1] >>> >> #[1] 2 3 4 5 6 7 8 9 10 >>> >> >>> >> 2) Are these right? They are at least surprising to me. >>> >> >>> >> (1:10)[-0] >>> >> #integer(0) >>> >> >>> >> (1:10)[-seq_len(0)] >>> >> #integer(0) >>> >> >>> >> >>> >> It was the last example that made me ask, seq_len(0) whould >>> avoid an >>> >> if/else or something similar. >>> > >>> > I think it's ok, because there is no negative zero integer, so -0 >>> is 0. >>> >>> Ok, this makes sense, I should have thought about that. >>> >>> > >>> > 1.0/-0L # Inf >>> > 1.0/-0.0 # - Inf >>> > >>> > And the same can be said for integer(0), which is the result of >>> > seq_len(0): there is no negative empty integer. >>> >>> I'm not completely convinced about this one, though. >>> I would expect -seq_len(n) to remove the first n elements from the >>> vector, therefore, when n == 0, it would remove none. >>> >>> And integer(0) is not the same as 0. >>> >>> (1:10)[-0] == (1:10)[0] == integer(0) # empty >>> >>> (1:10)[-seq_len(0)] == (1:10)[-integer(0)] >>> >>> >>> And I have just reminded myself to run >>> >>> identical(-integer(0), integer(0)) >>> >>> It returns TRUE so my intuition is wrong, R is right. >>> End of story. >>> >>> Thanks for the help, >>> >>> Rui Barradas >>> >>> > >>> > Iñaki >>> > >>> >> >>> >> >>> >> Thanks in advance, >>> >> >>> >> Rui Barradas >>> >> >>> >> ______________________________________________ >>> >> [hidden email] <mailto:[hidden email]> mailing >>> list >>> >> https://stat.ethz.ch/mailman/listinfo/r-devel >>> >>> ______________________________________________ >>> [hidden email] <mailto:[hidden email]> mailing list >>> https://stat.ethz.ch/mailman/listinfo/r-devel >>> >> >> ______________________________________________ >> [hidden email] mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel >> > ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
In reply to this post by Kenny Bell-2
El dom., 5 ago. 2018 a las 6:27, Kenny Bell (<[hidden email]>) escribió:
> > This should more clearly illustrate the issue: > > c(1, 2, 3, 4)[-seq_len(4)] > #> numeric(0) > c(1, 2, 3, 4)[-seq_len(3)] > #> [1] 4 > c(1, 2, 3, 4)[-seq_len(2)] > #> [1] 3 4 > c(1, 2, 3, 4)[-seq_len(1)] > #> [1] 2 3 4 > c(1, 2, 3, 4)[-seq_len(0)] > #> numeric(0) > Created on 2018-08-05 by the reprex package (v0.2.0.9000). IMO, the problem is that you are reading it sequentially: "-" remove "seq_" a sequence "len(0)" of length zero. But that's not how R works (how programming languages work in general). Instead, the sequence is evaluated in the first place, and then the sign may apply as long as you provided something that can hold a sign. And an empty element has no sign, so the sign is lost. Iñaki > > On Sun, Aug 5, 2018 at 3:58 AM Rui Barradas <[hidden email]> wrote: >> >> >> >> Às 15:51 de 04/08/2018, Iñaki Úcar escreveu: >> > El sáb., 4 ago. 2018 a las 15:32, Rui Barradas >> > (<[hidden email]>) escribió: >> >> >> >> Hello, >> >> >> >> Maybe I am not understanding how negative indexing works but >> >> >> >> 1) This is right. >> >> >> >> (1:10)[-1] >> >> #[1] 2 3 4 5 6 7 8 9 10 >> >> >> >> 2) Are these right? They are at least surprising to me. >> >> >> >> (1:10)[-0] >> >> #integer(0) >> >> >> >> (1:10)[-seq_len(0)] >> >> #integer(0) >> >> >> >> >> >> It was the last example that made me ask, seq_len(0) whould avoid an >> >> if/else or something similar. >> > >> > I think it's ok, because there is no negative zero integer, so -0 is 0. >> >> Ok, this makes sense, I should have thought about that. >> >> > >> > 1.0/-0L # Inf >> > 1.0/-0.0 # - Inf >> > >> > And the same can be said for integer(0), which is the result of >> > seq_len(0): there is no negative empty integer. >> >> I'm not completely convinced about this one, though. >> I would expect -seq_len(n) to remove the first n elements from the >> vector, therefore, when n == 0, it would remove none. >> >> And integer(0) is not the same as 0. >> >> (1:10)[-0] == (1:10)[0] == integer(0) # empty >> >> (1:10)[-seq_len(0)] == (1:10)[-integer(0)] >> >> >> And I have just reminded myself to run >> >> identical(-integer(0), integer(0)) >> >> It returns TRUE so my intuition is wrong, R is right. >> End of story. >> >> Thanks for the help, >> >> Rui Barradas >> >> > >> > Iñaki >> > >> >> >> >> >> >> Thanks in advance, >> >> >> >> Rui Barradas >> >> >> >> ______________________________________________ >> >> [hidden email] mailing list >> >> https://stat.ethz.ch/mailman/listinfo/r-devel >> >> ______________________________________________ >> [hidden email] mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
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