I've created a package in Mathematica but I can't seem to get Mathematica to read it in. The Package is of the form:
BeginPackage["name`"]
(function[]::usage)
Begin["`Private'"]
(functions)
End[]
EndPackage[]
I saved this file as a .m. The problem is that after I quit the kernel and then try to read in the package using Needs["name`"], I always get a no::cont error. I've tried saving the file in $BaseUserDirectory and $BaseDirectory, but it still give me a no::cont error:
Needs["name"]
Needs::nocont: "Context \!\(\"name\") was not created when Needs was evaluated."
I've also tried using the built-in File->Install function in Mathematica but it still gives me the same error. Is there something that I need to change with regards to the context?
Any help is much appreciated.
Thank you,
jm
Write the definitions in "Initialization Cells" when you create the package notebook. Otherwise they will be ignored. This worked for me with Version 9 on OS X. In previous versions it was probably not necessary, but I don't remember any more... :-)
It's because the directory of your package is not in $Path. Needs only searches the packages in $Path, while Get can search subdirectories.
Related
My understanding is that parallelization is included by default in a base Julia installation.
However, when I try to use it, I am getting errors that the functions and macros are not defined. For example:
nprocs()
Throws an error:
ERROR: UndefVarError: nprocs not defined
Stacktrace:
[1] top-level scope at none:0
Nowhere in any Julia documentation can I find mention of any packages that need to be included in order to use these functions. Am I missing something here?
I am using Julia version 1.0.5 inside the JuliaPro/Atom IDE
I figured it out. I'll leave this up for anyone else who is having this problem.
The solution is to import the Distributed package using:
using Distributed
Why this is not included in the documentation I do not know.
Once you know that nproc needs to be used, there exist a couple of options to find where it is defined.
A search through the documentation can help: https://docs.julialang.org/en/v1/search/?q=nprocs
Without leaving the Julia REPL, and even before nprocs gets imported in your session, you can use apropos in order to find more about it and determine that it is needed to import the Distributed package:
julia> apropos("nprocs")
Distributed.nprocs
Distributed.addprocs
Distributed.nworkers
An other way of using apropos is via the help REPL mode:
julia> # type `?` when the cursor is right after the prompt to enter help REPL mode
# note the use of double quotes to trigger "apropos" instead of a regular help query
help?> "nprocs"
Distributed.nprocs
Distributed.addprocs
Distributed.nworkers
Previous options work well in the case of nprocs because it is part of the standard library. JuliaHub is another option which allows looking for things more broadly, in the entire Julia ecosystem. As an example, looking for nprocs in JuliaHub's "Doc Search" tool also returns relevant results: https://juliahub.com/ui/Documentation?q=nprocs
This is meant to be a FAQ question, so please be as complete as possible. The answer is a community answer, so feel free to edit if you think something is missing.
This question was discussed and approved on meta.
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 been working on a programme to solve any maximisation LPP using the Revised Simplex Method. I have a problem with it though as I'm trying to input a sequence to solve the problem of non-basic variables.
My code is as follows:
matmax:=proc(tableau,basic)
local pivot,T,nbv,n,m,b;
T:=evalm(tableau);
n:=coldim(T); m:=rowdim(T);
b:=evalm(basic);
print(evalm(T));
nbv:={seq(i,i=2..n-1)}minus{seq(b[i],i=1..m)};
pivot:=getpiv(T,nbv);
while not pivot=FAIL do
b[pivot[1]]:=pivot[2];
T:=evalm(gauss(col(T,pivot[2]),pivot[1])&*T);
print(evalm(T));
nbv:={seq(i,i=2,..n-1)}minus{seq(b[i],i=1..m)};
pivot:=getpiv(T,nbv);
od;
[evalm(T),evalm(b)];
end;
The gauss and getpiv commands are procedures written to work in this programme, these work fine. However upon executing this procedure Maple returns with the message "Error, (in matmax) unable to execute seq" If anyone can give me any help on how to fix this problem it would be greatly appreciated.
If you have not loaded the linalg package before calling your matxmax then commands like coldim will simplify not work and not produce the integer results for n and m that are expected when using those in the bound of the seq calls. I believe that is why your seq error occurs, because n and m are not being assigned integer intermediate results like you expect.
You could try to remedy this by either loading the package before calling matmax, with with(linalg). But that is not so robust, and there are scenarios where it might not work. The with command won't work within a procedure body, so you can't put that inside the defn of proc matmax.
You could insert a line into matmax above, say, the local declaration line, like,
uses linalg;
That would make coldim and friends from the linalg package work. Unfortunately you've used the name pivot as a local variable, and that clashes with the pivot export from linalg package. So that simple fix via uses is not quite enough. You could use some name other than pivot, and that simple uses line, sure.
My own preference would be to make everything fully explicit, so that later on you or anyone else reading the code can understand it more clearly, even if it's longer. So I would use linalg[coldim] instead of coldim, and so on for the other exports uses from the linalg package within matmax.
Having said all the above, you should know that the linalg package is deprecated in modern Maple and that LinearAlgebra is the new package that offers the functionality you seem to be using. The command names are longer, but using the newer package means that you don't need all those evalm calls (or anything like it).
The problem could lie in your gauss and getpiv commands as they may not work with your procedure, could you expand on what they do?
so this week consisted of me installing Logtalk, one of the extensions for Prolog. In this case I'm using Prolog SWI, and I've run into a little snag. I'm not sure how to actually consult my own projects using Logtalk. I have taken a look at the examples that Logtalk comes with in order to understand the code itself, and in doing so I've been able to load them and execute them perfectly. What I don't understand though is what is actually going on when logtalk is loading a file, and how I can load my own projects.
I'll take the "hello_world" example as the point of discussion. The file called hello_world, is located in the examples folder of the Logtalk files. and yet it is consulted like so:
| ?- logtalk_load(hello_world(loader)).
First thing I thought was "that is a functor", looking at what it was doing using trace, I found that it was being called from the library and was being told how to get to the examples folder, where it then opened the "hello_world" folder and then the "loader" file. After which normal compiling happened.
I took a look at the library and couldn't figure out what was going on. I also thought that this can't possibly be the practical route to load user created projects in Logtalk. There was another post that was asking how to do this with SWI as well, but it didn't have any replies and didn't look like any effort had been made to figure the problem out.
Now let me be clear on something, I can use the "consult('...')." command just fine, I can even use "consult" to open my projects, however if I do this the logtalk console doesn't seem to be using any of the logtalk extensions and so is just vanilla prolog. I've used an installer for windows to install logtalk and I know that it is working as I've been looking at the examples that it comes with.
I've tried to find a tutorial but it is very difficult to find much of anything for Logtalk, the most I have found is this documentation on loading from within your project:
logtalk_load/1.
logtalk_load/2.
which I understand like so:
logtalk_load(file). % Top level loading
logtalk_load(folder(file). % Bottom level loading
So to save a huge manual load each time I would have a loader file that will load the other components of my project (which is what the examples for Logtalk do). This bit makes sense to me, I think, how I get to my loader file, doesn't.
Whether or not I have been understanding it correctly or not remains to be seen, but even if I have been understanding it correctly, I'm still lost as to how I load my own projects. Thanks for any help you can give, if you could give an example that'll be best as I do learn from examples quite quickly.
LITTLE UPDATE
You asked if I was using a logtalk console for my program running, and I am, I'm using the one that is provided and referred to during the "QUICK_START" file [Start > Programs > Logtalk > "Logtalk - Prolog-SWI (console)"] I thought to double check if the logtalk add ons were working and tested the "birds" example since it uses objects and is a nice familiar example. Yet again, everything works fine when using the logtalk_load/2 functor.
I took a look at what the library path was referring to a bit more given the feedback given so far. Looking into how logtalk loads files. Set up as it is so far, without changing things logtalk consults a folder which contains a prolog file called libpaths. It is basically how the examples are found, all it is is a part way description for where to get a file from. So when I say "logtalk_load/2" from what I can tell at least I'm going to this file and finding where the folder is that I'm asking for.
Now since I have already placed my own project folder in the examples folder, I promptly added my own folder to the list to test if this would at least be a part way solution to help me understand things a bit more. I added the following to the libpaths.pl file.
logtalk_library_path(my_project, examples('my_project/')).
% The path must end in a / so I have done so
So, I've got my folder path declared, got my folder, and the loader file is what I'll be calling when I use the loader. Without thinking about setting my own lib path folder, I should have enough to get things working and do some practical learning. But alas no, seems my investigation failed and I was returned the following:
ERROR: Unhandled exception: existence_error(library,project_aim)
Not what I wanted to see, I'm back to this library error business. I'm missing a reference to my project folder somewhere but I don't know where else it could need referencing. Running trace on the matter didn't help I simply had the following occur:
Call: (17) logtalk_library_path(my_project, _G943) ? creep
Fail: (17) logtalk_library_path(my_project, _G943) ? creep
ERROR: Unhandled exception: existence_error(library,my_project)
The call is failing, I'm simply not finding a reference where ever it is logtalk is looking. And I'm a novice at best when it comes to these sorts of issues, I've been using computers now for only 3 years and programming for the past 2 in visual studios using c# and c++. At least I've shone some more light on the matter, any more helpful advice given this information?
Please use the official Logtalk support channels for help in the future. You will get timely replies there. Daniel, thanks for providing help to this user.
I assume that you're using Logtalk 2.x. Note that Logtalk 3.x supports relative and full source file paths. In Logtalk 2.x, the logtalk_compile/1-2 (compile to disk) and logtalk_load/1-2 (compile and load into memory) predicates take either the name of a source file (without the .lgt extension) OR the location of the source file to be loaded using "library notation". To use the former you need first to change the current working directory to the directory containing the file. This makes the second option more flexible. As you mention, the hello_world example you cite, can be loaded by typing:
?- logtalk_load(hello_world(loader)).
or:
?- {hello_world(loader)}.
Logtalk 2.x and 3.x also provide integration with some SWI-Prolog features such as consult/1, make/0, edit/0-1, the graphical tracer and the graphical profiler. For example:
?- [hello_world(loader)].
********** Hello World! **********
% [ /Users/pmoura/logtalk/examples/hello_world/hello_world.lgt loaded ]
% [ /Users/pmoura/logtalk/examples/hello_world/loader.lgt loaded ]
% (0 warnings)
true.
To load your own examples and projects, the easiest way is to add a library path to the directory holding your files to the $LOGTALKUSER/settings.lgt file (%LOGTALKUSER%\settings.lgt on Windows) as Daniel explained. The location of the Logtalk user directory is defined by you when using the provided installer. The default is My Documents\Logtalk in Windows. Editing the libpaths.pl file is not a good idea. Use the settings.lgt file preferentially to define your own library paths. Assuming, as it seems to be your case, that you have created a %LOGTALKUSER%\examples\project_aim directory, add the following lines to your %LOGTALKUSER%\settings.lgt file:
:- multifile(logtalk_library_path/2).
:- dynamic(logtalk_library_path/2).
logtalk_library_path(project_aim, examples('project_aim/').
If you have a %LOGTALKUSER%\examples\project_aim\loader.lgt file, you can then load it by typing:
?- {project_aim(loader)}.
Hope this helps.
What makes me uncertain of my answer is just that you claim the usual consult works but not logtalk_load. You do have to run a different program to get to Logtalk than Prolog. In Unix it would be something like swilgt for SWI-Prolog or gplgt for GNU Prolog. I don't have Windows so I can't really tell you what you need to do there, other than maybe make sure you're running a binary named Logtalk and not simply Prolog.
Otherwise I think your basic problem is that in Windows it's hard to control your working directory. In a Unix environment, you'd navigate your terminal over to the directory with your files in it and launch Logtalk or Prolog from there. Then when you name your files they would be in the current directory, so Prolog would have no trouble finding them. If you're running a command-line Prolog, you can probably configure the menu item so that it will do this for you, but you have to know where you want to send it.
You can use the functor notation either to get at subdirectories (so, e.g., foo(bar(baz(bat(afile)))) finds foo\bar\baz\bat\afile.lgt). This you seemed to have figured out, and I can at least corroborate it. This will search in its predefined list of functors, and also in the current directory. But you could launch Logtalk from anywhere and then run, say, assertz(logtalk_library_path(foo, 'C:\foo\bar\baz\bat')). after which logtalk_load(foo(afile)) is going to be expanded to C:\foo\bar\baz\bat\afile.lgt.
Building on that technique, you could put your files in the Logtalk user directory and use $LOGTALKUSER as demonstrated in the documentation. I can't find a definitive reference on where the Logtalk user directory will be on Windows, but I would expect it to be in the Documents and Settings folder for your user. So you could put stuff in there and reference it by defining a new logtalk_library_path like this.
It's nice, but it still leaves you high and dry if you have to keep on re-entering these assertions every time you launch. Fortunately, there is a Logtalk settings file named settings.lgt in your Logtalk user directory which has a chunk of commented-out code near the top:
% To define a "library" path for your projects, edit and uncomment the
% following lines (the library path must end with a slash character):
/*
:- multifile(logtalk_library_path/2).
:- dynamic(logtalk_library_path/2).
logtalk_library_path(my_project, '$HOME/my_project/').
logtalk_library_path(my_project_examples, my_project('examples/')).
*/
You can simply uncomment those lines and insert your own stuff to get a persistent shortcut.
You can also write a plrc file for SWI Prolog to define other things to happen at startup. The other option seems cleaner since it's Logtalk-specific, but a plrc is more general.
Once you have that machinery in place, having a loader file will be a lot more helpful.
NOTE: I don't have Windows to test any of this stuff on, so you may need to make either or both of the following changes to the preceeding:
You may need to use / instead of \ in your paths (or maybe either will work, who knows?). I'd probably try / first because that's how all other systems work.
You may need to use %LOGTALKUSER% instead of $LOGTALKUSER, depending on how Logtalk expands variables.
Hope this helps and I hope you stick with Logtalk, it could use some passionate users like yourself!
I just installed the scheme48 package from macports and have started experiencing. I was watching this youtube video, link here and was attempting to perform some of the examples. In the lecture the professor is running scheme on a Sun terminal. For example, I attempt to do '(first 473)' and get 'Error: undefined variable first'. Now, I'm assuming I haven't loaded the correct package / library or what ever it is called in scheme but am not sure what the syntax and library is. I believe that scheme48 and the scheme version on that sun terminal in the video are not the same and could be part of the problem.
So, what library do I need to use and how do I load it?
Those lecture notes are based on a book called Simply Scheme, and you can find the library code that is used in the book here. Specifically, you need simply.scm.
(But whether it is a good idea to have these kind of overloading functions is debatable. Specifically, note that first is used in a way that is different from many other languages.)