Could someone please explain the following? I did check bug reports, but
did not recognize the issue there. I am reluctant to call it a bug, as it is much more likely my misunderstanding. Ergo my request for clarification: ## As expected: > lapply(1:3, rnorm, n = 3) [[1]] [1] 2.481575 1.998182 1.312786 [[2]] [1] 2.858383 1.827863 1.699015 [[3]] [1] 1.821910 2.530091 3.995677 ## Unexpected by me: > lapply(1:3, runif, n = 3) [[1]] [1] 1 1 1 [[2]] [1] NaN NaN NaN [[3]] [1] NaN NaN NaN Warning messages: 1: In FUN(X[[i]], ...) : NAs produced 2: In FUN(X[[i]], ...) : NAs produced ## But note, as expected: > lapply(1:3, function(x)runif(3)) [[1]] [1] 0.2950459 0.8490556 0.4303680 [[2]] [1] 0.5961144 0.5330914 0.2363679 [[3]] [1] 0.8079495 0.1431838 0.3671915 Many thanks for any clarification. -- Bert [[alternative HTML version deleted]] ______________________________________________ [hidden email] 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. |
Hi Bert,
On Tue, Nov 14, 2017 at 8:11 PM, Bert Gunter <[hidden email]> wrote: > Could someone please explain the following? I did check bug reports, but > did not recognize the issue there. I am reluctant to call it a bug, as it > is much more likely my misunderstanding. Ergo my request for clarification: > > ## As expected: > >> lapply(1:3, rnorm, n = 3) > [[1]] > [1] 2.481575 1.998182 1.312786 > > [[2]] > [1] 2.858383 1.827863 1.699015 > > [[3]] > [1] 1.821910 2.530091 3.995677 > Exactly what expectation do you imagine the above is consistent with? Does > lapply(100*(1:3), rnorm, n = 3) [[1]] [1] 100.35425 99.29429 98.69429 [[2]] [1] 198.2963 201.1031 201.1077 [[3]] [1] 299.7012 298.3700 298.0684 change your assessment? > > ## Unexpected by me: > >> lapply(1:3, runif, n = 3) > [[1]] > [1] 1 1 1 > > [[2]] > [1] NaN NaN NaN > > [[3]] > [1] NaN NaN NaN > > Warning messages: > 1: In FUN(X[[i]], ...) : NAs produced > 2: In FUN(X[[i]], ...) : NAs produced The first argument to runif is named 'n'. Thus, lapply(1:3, runif) means roughly list(runif(n = 1), runif(n = 2), runif(n = 3)) But you specify than lapply(1:3, runif, n = 3). Since the first argument ('n') is already specified, the X values from lapply get "pushed" to the second argument. That is, lapply(1:3, runif, n = 3) means roughly list(runif(n = 3, min = 1), runif(n = 3, min = 2), runif(n = 3, min = 3)) Note that this is exactly the same thing that happens with lapply(1:3, rnorm, n = 3), though it becomes more obvious with lapply(100*(1:3), rnorm, n = 3) That is, lapply(1:3, rnorm, n = 3) means roughly list(rnorm(n = 3, mean = 1), rnorm(n = 3, mean = 2), rnorm(n = 3, mean = 3)) > > > ## But note, as expected: > >> lapply(1:3, function(x)runif(3)) > [[1]] > [1] 0.2950459 0.8490556 0.4303680 > > [[2]] > [1] 0.5961144 0.5330914 0.2363679 > > [[3]] > [1] 0.8079495 0.1431838 0.3671915 Sure, because you never use x in the body of your anonymous function. As a final note, what you seem to expect can be achieved with replicate(3, rnorm(n = 3), simplify = FALSE) and replicate(3, runif(n = 3), simplify = FALSE) Best, Ista > > > > Many thanks for any clarification. > > -- Bert > > [[alternative HTML version deleted]] > > ______________________________________________ > [hidden email] 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. ______________________________________________ [hidden email] 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. |
Thanks, Ista. That explains it.
What I missed is the following "note" in ?lapply: "This means that the recorded call is always of the form FUN(X[[i]], ...), with i replaced by the current (integer or double) index. " That being the case, X[[i]] gets passed to the first available argument, which for runif(n=3, min, max) is the min argument, as you said. This is a subtlety (to me, anyway) of which I was unaware. Which is why I hesitated to call it a bug. It ain't! It is documented -- I just failed to read carefully enough. Cheers, Bert Bert Gunter "The trouble with having an open mind is that people keep coming along and sticking things into it." -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) On Tue, Nov 14, 2017 at 6:11 PM, Ista Zahn <[hidden email]> wrote: > Hi Bert, > > On Tue, Nov 14, 2017 at 8:11 PM, Bert Gunter <[hidden email]> > wrote: > > Could someone please explain the following? I did check bug reports, but > > did not recognize the issue there. I am reluctant to call it a bug, as it > > is much more likely my misunderstanding. Ergo my request for > clarification: > > > > ## As expected: > > > >> lapply(1:3, rnorm, n = 3) > > [[1]] > > [1] 2.481575 1.998182 1.312786 > > > > [[2]] > > [1] 2.858383 1.827863 1.699015 > > > > [[3]] > > [1] 1.821910 2.530091 3.995677 > > > > Exactly what expectation do you imagine the above is consistent with? Does > > > lapply(100*(1:3), rnorm, n = 3) > [[1]] > [1] 100.35425 99.29429 98.69429 > > [[2]] > [1] 198.2963 201.1031 201.1077 > > [[3]] > [1] 299.7012 298.3700 298.0684 > > change your assessment? > > > > > ## Unexpected by me: > > > >> lapply(1:3, runif, n = 3) > > [[1]] > > [1] 1 1 1 > > > > [[2]] > > [1] NaN NaN NaN > > > > [[3]] > > [1] NaN NaN NaN > > > > Warning messages: > > 1: In FUN(X[[i]], ...) : NAs produced > > 2: In FUN(X[[i]], ...) : NAs produced > > The first argument to runif is named 'n'. Thus, > > lapply(1:3, runif) > > means roughly > > list(runif(n = 1), runif(n = 2), runif(n = 3)) > > But you specify than lapply(1:3, runif, n = 3). Since the first > argument ('n') is already specified, the X values from lapply get > "pushed" to the second argument. That is, > > lapply(1:3, runif, n = 3) > > means roughly > > list(runif(n = 3, min = 1), runif(n = 3, min = 2), runif(n = 3, min = 3)) > > Note that this is exactly the same thing that happens with > > lapply(1:3, rnorm, n = 3), though it becomes more obvious with > > lapply(100*(1:3), rnorm, n = 3) > > That is, > > lapply(1:3, rnorm, n = 3) > > means roughly > > list(rnorm(n = 3, mean = 1), rnorm(n = 3, mean = 2), rnorm(n = 3, mean = > 3)) > > > > > > > ## But note, as expected: > > > >> lapply(1:3, function(x)runif(3)) > > [[1]] > > [1] 0.2950459 0.8490556 0.4303680 > > > > [[2]] > > [1] 0.5961144 0.5330914 0.2363679 > > > > [[3]] > > [1] 0.8079495 0.1431838 0.3671915 > > Sure, because you never use x in the body of your anonymous function. > > As a final note, what you seem to expect can be achieved with > > replicate(3, rnorm(n = 3), simplify = FALSE) > > and > > replicate(3, runif(n = 3), simplify = FALSE) > > > Best, > Ista > > > > > > > > > Many thanks for any clarification. > > > > -- Bert > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > [hidden email] 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]] ______________________________________________ [hidden email] 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. |
In reply to this post by Bert Gunter-2
Your lapply is making the call
runif(n=3, min=i) for i in 1:3. That runif's 3 argument is 'max', with default value 1 so that is equivalent to calling runif(n=3, min=i, max=1) When i>max, outside the domain of the family of uniform distributions, runif returns NaN's. Bill Dunlap TIBCO Software wdunlap tibco.com On Tue, Nov 14, 2017 at 5:11 PM, Bert Gunter <[hidden email]> wrote: > Could someone please explain the following? I did check bug reports, but > did not recognize the issue there. I am reluctant to call it a bug, as it > is much more likely my misunderstanding. Ergo my request for clarification: > > ## As expected: > > > lapply(1:3, rnorm, n = 3) > [[1]] > [1] 2.481575 1.998182 1.312786 > > [[2]] > [1] 2.858383 1.827863 1.699015 > > [[3]] > [1] 1.821910 2.530091 3.995677 > > > ## Unexpected by me: > > > lapply(1:3, runif, n = 3) > [[1]] > [1] 1 1 1 > > [[2]] > [1] NaN NaN NaN > > [[3]] > [1] NaN NaN NaN > > Warning messages: > 1: In FUN(X[[i]], ...) : NAs produced > 2: In FUN(X[[i]], ...) : NAs produced > > > ## But note, as expected: > > > lapply(1:3, function(x)runif(3)) > [[1]] > [1] 0.2950459 0.8490556 0.4303680 > > [[2]] > [1] 0.5961144 0.5330914 0.2363679 > > [[3]] > [1] 0.8079495 0.1431838 0.3671915 > > > > Many thanks for any clarification. > > -- Bert > > [[alternative HTML version deleted]] > > ______________________________________________ > [hidden email] 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]] ______________________________________________ [hidden email] 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. |
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