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I am using R and tried some.function but I got following error message:
Error: could not find function "some.function"
This question comes up very regularly. When you get this type of error in R, how can you solve it?
There are a few things you should check :
Did you write the name of your function correctly? Names are case sensitive.
Did you install the package that contains the function? install.packages("thePackage") (this only needs to be done once)
Did you attach that package to the workspace ?
require(thePackage) (and check its return value) or library(thePackage) (this should be done every time you start a new R session)
Are you using an older R version where this function didn't exist yet?
Are you using a different version of the specific package? This could be in either direction: functions are added and removed over time, and it's possible the code you're referencing is expecting a newer or older version of the package than what you have installed.
If you're not sure in which package that function is situated, you can do a few things.
If you're sure you installed and attached/loaded the right package, type help.search("some.function") or ??some.function to get an information box that can tell you in which package it is contained.
find and getAnywhere can also be used to locate functions.
If you have no clue about the package, you can use findFn in the sos package as explained in this answer.
RSiteSearch("some.function") or searching with rdocumentation or rseek are alternative ways to find the function.
Sometimes you need to use an older version of R, but run code created for a newer version. Newly added functions (eg hasName in R 3.4.0) won't be found then. If you use an older R version and want to use a newer function, you can use the package backports to make such functions available. You also find a list of functions that need to be backported on the git repo of backports. Keep in mind that R versions older than R3.0.0 are incompatible with packages built for R3.0.0 and later versions.
Another problem, in the presence of a NAMESPACE, is that you are trying to run an unexported function from package foo.
For example (contrived, I know, but):
> mod <- prcomp(USArrests, scale = TRUE)
> plot.prcomp(mod)
Error: could not find function "plot.prcomp"
Firstly, you shouldn't be calling S3 methods directly, but lets assume plot.prcomp was actually some useful internal function in package foo. To call such function if you know what you are doing requires the use of :::. You also need to know the namespace in which the function is found. Using getAnywhere() we find that the function is in package stats:
> getAnywhere(plot.prcomp)
A single object matching ‘plot.prcomp’ was found
It was found in the following places
registered S3 method for plot from namespace stats
namespace:stats
with value
function (x, main = deparse(substitute(x)), ...)
screeplot.default(x, main = main, ...)
<environment: namespace:stats>
So we can now call it directly using:
> stats:::plot.prcomp(mod)
I've used plot.prcomp just as an example to illustrate the purpose. In normal use you shouldn't be calling S3 methods like this. But as I said, if the function you want to call exists (it might be a hidden utility function for example), but is in a namespace, R will report that it can't find the function unless you tell it which namespace to look in.
Compare this to the following:
stats::plot.prcomp
The above fails because while stats uses plot.prcomp, it is not exported from stats as the error rightly tells us:
Error: 'plot.prcomp' is not an exported object from 'namespace:stats'
This is documented as follows:
pkg::name returns the value of the exported variable name in namespace pkg, whereas pkg:::name returns the value of the internal variable name.
I can usually resolve this problem when a computer is under my control, but it's more of a nuisance when working with a grid. When a grid is not homogenous, not all libraries may be installed, and my experience has often been that a package wasn't installed because a dependency wasn't installed. To address this, I check the following:
Is Fortran installed? (Look for 'gfortran'.) This affects several major packages in R.
Is Java installed? Are the Java class paths correct?
Check that the package was installed by the admin and available for use by the appropriate user. Sometimes users will install packages in the wrong places or run without appropriate access to the right libraries. .libPaths() is a good check.
Check ldd results for R, to be sure about shared libraries
It's good to periodically run a script that just loads every package needed and does some little test. This catches the package issue as early as possible in the workflow. This is akin to build testing or unit testing, except it's more like a smoke test to make sure that the very basic stuff works.
If packages can be stored in a network-accessible location, are they? If they cannot, is there a way to ensure consistent versions across the machines? (This may seem OT, but correct package installation includes availability of the right version.)
Is the package available for the given OS? Unfortunately, not all packages are available across platforms. This goes back to step 5. If possible, try to find a way to handle a different OS by switching to an appropriate flavor of a package or switch off the dependency in certain cases.
Having encountered this quite a bit, some of these steps become fairly routine. Although #7 might seem like a good starting point, these are listed in approximate order of the frequency that I use them.
If this occurs while you check your package (R CMD check), take a look at your NAMESPACE.
You can solve this by adding the following statement to the NAMESPACE:
exportPattern("^[^\\\\.]")
This exports everything that doesn't start with a dot ("."). This allows you to have your hidden functions, starting with a dot:
.myHiddenFunction <- function(x) cat("my hidden function")
I had the error
Error: could not find function some.function
happen when doing R CMD check of a package I was making with RStudio. I found adding
exportPattern(".")
to the NAMESPACE file did the trick. As a sidenote, I had initially configured RStudio to use ROxygen to make the documentation -- and selected the configuration where ROxygen would write my NAMESPACE file for me, which kept erasing my edits. So, in my instance I unchecked NAMESPACE from the Roxygen configuration and added exportPattern(".") to NAMESPACE to solve this error.
This error can occur even if the name of the function is valid if some mandatory arguments are missing (i.e you did not provide enough arguments).
I got this in an Rcpp context, where I wrote a C++ function with optionnal arguments, and did not provided those arguments in R. It appeared that optionnal arguments from the C++ were seen as mandatory by R. As a result, R could not find a matching function for the correct name but an incorrect number of arguments.
Rcpp Function : SEXP RcppFunction(arg1, arg2=0) {}
R Calls :
RcppFunction(0) raises the error
RcppFunction(0, 0) does not
Rdocumentation.org has a very handy search function that - among other things - lets you find functions - from all the packages on CRAN, as well as from packages from Bioconductor and GitHub.
If you are using parallelMap you'll need to export custom functions to the slave jobs, otherwise you get an error "could not find function ".
If you set a non-missing level on parallelStart the same argument should be passed to parallelExport, else you get the same error. So this should be strictly followed:
parallelStart(mode = "<your mode here>", N, level = "<task.level>")
parallelExport("<myfun>", level = "<task.level>")
You may be able to fix this error by name spacing :: the function call
comparison.cloud(colors = c("red", "green"), max.words = 100)
to
wordcloud::comparison.cloud(colors = c("red", "green"), max.words = 100)
I got the same, error, I was running version .99xxx, I checked for updates from help menu and updated My RStudio to 1.0x, then the error did not come
So simple solution, just update your R Studio
I’ve the following code which require multiple packages in cmd package
PATH_SEP = string(os.PathSeparator)
my project structure is like following
go/src/my proj
-cmd
--runners
--otherpackage
-- package2
-- constants
--….
in constants i put the code
PATH_SEP = string(os.PathSeparator)
const2 etc
and in runners and package2/3 etc I use this constant.
is it OK ? otherwise I need to duplicate the code for other packages .
I would suggest to declare struct with constant fields and import that struct in any package you wants to use the constants.
package cmd
type Constants struct{
const1 int
const2 int
}
It would be better to have a separate file for constants. Create a file called global.go which contains all constant structs to be used in different packages that way your code would be cleaner.
Note: We require constants to be shared in multiple files, so it will be better to import the package containing constants. Rather than package containing methods and other details even if we do not need them.
You can use the constants as you describe, there is nothing wrong with it. But it is less intuitive.
How i would go about this is having a root package constants and those can be used anywhere in the project.
go/src/my proj
-cmd
-constants
--runners
--otherpackage
--package2
--….
I've project done in C++ where I used #define macros to give a name of the project, which I used in several places, I don't change this name often but sometimes I may need to change this, then I change this macro and rebuild my code. Now I'm converting this code to Go. Can someone suggest me how to implement this in Go? I'm not interested in using global variables for this purpose because I've many such macros and I doubt this cause my project to occupy more cpu and effect the performance.
Luckily, Go does not support macros.
There are two venues in Go to implement what is done using macros
in other programming languages:
"Meta-programming" is done using code generation.
"Magic variables/constants" are implemented using "symbol substitutions"
at link time.
It appears, the latter is what you're after.
Unfortunately, the help on this feature is nearly undiscoverable
on itself, but it explained in the output of
$ go tool link -help
To cite the relevant bit from it:
-X definition
add string value definition of the form importpath.name=value
So you roll like this:
In any package, where it is convenient,
you define a string constant the value of which you'd like to change at build time.
Let's say, you define constant Bar in package foo.
You pass a special flag to the go build or go install invocation for the linking phase at compile time:
$ go install -ldflags='-X foo.Bar="my super cool string"'
As the result, the produced binary will have the constant foo.Bar
set to the value "my super cool string" in its "read-only data" segment,
and that value will be used by the program's code.
See also the go help build output about the -ldflags option.
Go doesn't support Macros.
but you can use a constants inside a package and refer it where ever you need.
package constant
// constants.go file
const (
ProjectName = "My Project"
Title = "Awesome Title"
)
and in your program
package main
import "<path to project>/constant" // replace the path to project with your path from GOPATH
func main() {
fmt.Println(constant.ProjectName)
}
The project structure would be
project
|- constant
| |- constants.go
|-main.go
In my early days of learning Go and trying to use package github.com/jessevdk/go-flags. I checked the Fly example referenced in another go-flags thread, but it apparently does not use AddCommand (at least per my grep).
The godoc article recommends defining a global parser instance and to implement each command in a separate file. Each of those command files should define a go init function which calls AddCommand on the global parser.
Making my parser global was easy enough. Confused on the init() setups:
1) My understanding is that init() order execution is random, other than your main's init running last.
2) If so, I can't ensure that my NewParser() call in my configuration code has been called prior my AddCommand() calls.
3) My code compiles, but a --help doesn't show any defined commands, making me think that indeed, the AddCommand() was called before the NewParser()
/* Just a guess */
4) QED I'm confused!
Does anybody have a recommended example I could go learn from?
I am currently writing ExampleFuncs in my Go test scripts. For example:
package hello
import "testing"
func ExampleGetSymbol() {
data := GetSymbol("AAPL")
fmt.Println(len(data.Data))
// Output: 21
}
Now, this gives me two benefits:
This example is executed when I am running go test and
It appears in the godoc documentation under func GetSymbol
One thing bothers me and I am wondering if there is anything I should do about it.
For the user that's trying to learn from this example, the line
data := GetSymbol("AAPL")
should actually be
data := hello.GetSymbol("AAPL")
but since the test is in the same scope as the package, I cannot use it like this.
So I guess the distilled version of my question would be:
Is there a way to allow package.field notation inside the package scope?
Thanks in advance
Rather than putting this in package hello, put it in package hello_test. You're allowed to have both hello and hello_test packages in the same directory, and it allows (requires) you to create your examples the way you're suggesting.
Incidentally, this also causes you to write your test cases (at least for this file) only to the public API. This is often a good thing. But if you need to write to private functions, you can split your tests into separate files, some in the hello package and some in hello_test.
BTW, documentation for this is slightly buried. You can find it in the "Test packages" section of the go cmd documentation.