rfunctions | a set of R functions | Functional Programming library
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kandi X-RAY | rfunctions Summary
some cool R functions that I either wrote, stole, or modified.
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QUESTION
Motivation: I want to write an interface that uses questions from the R package exams in learnr questions/quizzes. In R/exams each question is either an R/Markdown (Rmd) or R/LaTeX (Rnw) file with a certain structure specifying question, solution, and further meta-information. The questions can contain R code to make them dynamic, e.g., sampling numbers or certain text building blocks etc. Hence, the workflow is that first the questions are run through knitr::knit
or utils::Sweave
and then embedded in a suitable output format.
Problem: When I rmarkdown::run("learnr+rexams.Rmd")
a learnr tutorial that dynamically produces a question or quiz from an Rmd exercise I get the error:
Error in if (grepl(not_valid_char_regex, label)) { : argument is of length zero
The code for a simple reproducible example learnr+rexams.Rmd
is included below.
The reason for the error appears to be that learnr runs a function verify_tutorial_chunk_label()
that tries to assure the the learnr R chunk labels are well formatted. However, confusion is caused by the chunks that are run by the R/exams package, unnecessarily leading to the error above.
Workarounds: I can disable the verify_tutorial_chunk_label()
in the learnr namespace and then everything works well. Or I can use Rnw instead of Rmd exercises and then learnr does not conflict with Sweave()
. Also, when I run my code outside of a learnr tutorial it works fine.
Question: Can I do anything less invasive to make exams
cooperate with learnr
? For example, setting some appropriate knitr
options or something like that?
Example: This is the source for the minimal learnr tutorial learnr+rexams.Rmd
that replicates the problem. Note that everything is very much simplified and only works for certain R/exams exercises, here using the function exercise template that ships with R/exams.
ANSWER
Answered 2021-Apr-14 at 21:10The problem is that by the time learnr::question()
is called, knitr is no longer able to find the chunk label for the chunk where exams2learnr()
was called. You can get around this by setting the current chunk label before calling do.call(learnr_question, x)
:
QUESTION
This, as this other question is related to Issue #29, but I haven't been able to get it to work.
I would like to have images, css, .js and .R files stored in different folders that I can then use in multiple presentations. And i'd like to store the .Rmd files in individual subfolders. Like so:
...ANSWER
Answered 2019-Apr-24 at 07:43You can simply link to them in the corresponding fields. To go one directory up, you can use ../
.
QUESTION
I was wondering whether Coq defined the real numbers as Cauchy sequences or Dedekind cuts, so I checked Coq.Reals.Raxioms and... none of these two. The real numbers are axiomatized, along with their operations (as Parameter
s and Axiom
s). Why is it so?
Also, the real numbers tightly rely on the notion of subset, since one of their defining properties is that is every upper bounded subset has a least upper bound. The Axiom completeness
encodes those subsets as Prop
s.
I have the impression that these Prop
s only form the definable subsets of the reals. So does Coq only have access to definable real numbers? What exactly is this Coq's R
? Analytical numbers? Algebraic numbers? Arithmetical numbers?
If, as I suspect, Coq only has a countable subset of the reals (because there are only countably many Prop
s), that makes an infinitesimal part of the reals. Is it fit for theories that deeply exploit the structure of the ZFC real numbers, such as fractals, chaos theory or the Lebesgue measure?
EDIT
Here is a naive construction of the reals by Dedekind cuts.
...ANSWER
Answered 2018-Aug-20 at 23:00In ZFC, the real numbers satisfy two useful properties:
there is a function
e : R * R -> bool
that returns true if and only if its two arguments are equal, andthe order relation is antisymmetric: if
x <= y
andy <= x
, thenx = y
.
Both of these properties would fail in Coq if the real numbers were defined without additional axioms in terms of Cauchy sequences or Dedekind cuts. For example, a Dedekind cut can be defined as a pair of predicates P Q : rational -> Prop
that satisfy certain properties. It is impossible to write a Coq function that decides whether two cuts are equal, because equality of predicates on rationals is undecidable. And any reasonable notion of ordering on cuts would fail to satisfy antisymmetry because equality on predicates is not extensional: it is not the case that forall x, P x <-> Q x
implies P = Q
.
As for your second question, it is true that there can be only countably many Coq terms of type R -> Prop
. However, the same is true of ZFC: there are only countably many formulas for defining subsets of the real numbers. This is connected to the Löwenheim-Skolem paradox, which implies that if ZFC is consistent it has a countable model -- which, in particular, would have only countably many real numbers. Both in ZFC and in Coq, however, it is impossible to define a function that enumerates all real numbers: they are countable from our own external perspective on the theory, but uncountable from the theory's point of view.
QUESTION
I have a df:
...ANSWER
Answered 2017-Jun-22 at 16:30I used dplyr
however result for plot3 is different and I dont know why. Could you provide your results for each calculations or check mine and let me know where the mistake is?
Also. If your are interested in calculating diversity indices you can get familiar with vegan
package and especially diversity()
function
QUESTION
I have a program that uses string functions and requires to compile with c++0x.But I can't figure out how/where to put "-std=c++0x" my flag. I've only compiled using basic commands within makefile, so this is new to me. Here is my current makefile without the flag.
...ANSWER
Answered 2017-May-07 at 16:44You can define CXXFLAGS in your make file:
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