Questions tagged [julia]
The Julia programming language is fast, expressive and dynamic. By aggressively targeting technical computing it has become a robust general purpose language. It addresses the two-language problem by combining the ease of use of high-level languages such as R and Python with the performance of C and Fortran.
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What is a "symbol" in Julia?
Specifically:
I am trying to use Julia's DataFrames package, specifically the readtable() function with the names option, but that requires a vector of symbols.
what is a symbol?
why would they ...
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Linking R and Julia?
Julia looks very promising for fast and syntax-sane computation (e.g. here), but I suspect it will not be anywhere near R in terms of overall statistics workflow for some time yet. So I'd like to use ...
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Is Julia dynamically typed?
A lot of blogs, and the manual itself, say that Julia is dynamically typed.
But from my reading of the manual, it sounds to me more like it is
statically typed with type inference, like F#.
Is Julia ...
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How to make user defined function descriptions ("docstrings") available to julia REPL?
How can user defined functions (say f) have meaningful printouts when inspected via the REPL using ?for help(f)
For example imagine I write the following funciton
function f(x::Float64, y::Float64)
...
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Running Julia .jl files
I'm new to julia and just finished my first program. I wrote the code in julia-studio and have been testing it within that program. It gives me all of the correct output, but the shell separates the ...
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How can I dispatch on traits relating two types, where the second type that co-satisfies the trait is uniquely determined by the first?
Say I have a Julia trait that relates to two types: one type is a sort of "base" type that may satisfy a sort of partial trait, and the other is an associated type that is uniquely ...
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What is the difference between `using` and `import` in Julia when building a module?
Question: What is the difference between using and import in Julia when I'm building my own module?
My guess based on reading the docs: using is used to bring another module into the name-space of ...
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Speeding up Julia's poorly written R examples
The Julia examples to compare performance against R seem particularly convoluted. https://github.com/JuliaLang/julia/blob/master/test/perf/perf.R
What is the fastest performance you can eke out of ...
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In Julia, why is @printf a macro instead of a function?
In Julia, the syntax to print a formatted string is as follows:
@printf("Hello %d\n", 5)
Why is @printf a macro instead of a function? Is it so that it can accept a varying number of arguments?
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Get a list of current variables in Julia Lang
I am new to Julia Lang. I am coming from the background of Matlab.
In Matlab, when pressing whos command I will get all variables in the current scope; and also, I can store them in another variable ...
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Julia compiles the script every time?
Julia language compiles the script every time, can't we compile binaries with julia instead?
I tried a small helloworld script with println function it took 2 to 3 seconds for julia to show the output!...
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How do I reload a module in an active Julia session after an edit?
2018 Update: Be sure to check all the responses, as the answer to this question has changed multiple times over the years. At the time of this update, the Revise.jl answer is probably the best ...
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How to upgrade Julia to a new release?
I'm using v"0.3.8" on Windows. I found from
http://julialang.org/downloads/
Current Release (v0.3.9)
I know I could download the prebuild version and install again. Is there a way to ...
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Julia: OOP or not
I'm working on Juno with Julia.
I don't know if Julia supports OOP or not.
For example, is there something like class or struct of c++?
How to declare it with members such as a data or a function?
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How to import custom module in julia
I have a module I wrote here:
# Hello.jl
module Hello
function foo
return 1
end
end
and
# Main.jl
using Hello
foo()
When I run the Main module:
$ julia ./Main.jl
I get this error:...
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Access command line arguments in Julia
When I type in
$ julia myprog.jl foo bar baz
Where in my code can I go to access the strings "foo", "bar", "baz" ?
I'm looking for the Python equivalent of sys.argv
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Parallelism in Julia: Native Threading Support
In their arXiv paper, the original authors of Julia mention the following:
2.14 Parallelism.
Parallel execution is provided by a message-based multi-processing system implemented in Julia in ...
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In what sense are languages like Elixir and Julia homoiconic?
Homoiconicity in Lisp is easy to see:
(+ 1 2)
is both the function call to + with 1, 2 as arguments, as well as being a list containing +, 1, and 2. It is simultaneously both code and data.
In a ...
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None value in Julia
What is the Julia equivalent of the None value in Python? (As shown here in built-in constants.)
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What is the recommended way to iterate a matrix over rows?
Given a matrix m = [10i+j for i=1:3, j=1:4], I can iterate over its rows by slicing the matrix:
for i=1:size(m,1)
print(m[i,:])
end
Is this the only possibility? Is it the recommended way?
And ...
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Is the Julia language really as fast as it claims?
Following this post I decided to benchmark Julia against GNU Octave and the results were inconsistent with the speed-ups illustrated in julialang.org.
I compiled both Julia and GNU Octave with ...
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Generating a random integer in range in Julia
I am migrating from MATLAB to Julia and I am trying to generate a random integer in range 1:n.
For n < 21,
rand(r[1:n]) works.
However for n > 20, for example, rand(r[1:21]), I get this message:
...
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Julia: append to an empty vector
I would like to create an empty vector and append to it an array in Julia. How do I do that?
x = Vector{Float64}
append!(x, rand(10))
results in
`append!` has no method matching append!(::Type{...
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How to install Julia in an anaconda environment?
One of the main features of Anaconda is that it is language agnostic as stated in their blog:
You can create environments of any binary dependency tree (different
versions of Python, R, Julia, ...
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julia create an empty dataframe and append rows to it
I am trying out the Julia DataFrames module. I am interested in it so I can use it to plot simple simulations in Gadfly. I want to be able to iteratively add rows to the dataframe and I want to ...
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Concatenating arrays in Julia
If the two Int arrays are, a = [1;2;3] and b = [4;5;6], how do we concatenate the two arrays in both the dimensions? The expected outputs are,
julia> out1
6-element Array{Int64,1}:
1
2
3
4
5
...
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What does an exclamation mark mean after the name of a function?
I saw a function like this
function operator!(c::Matrix, out::Matrix)
......
end
What does ! mean here?
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What's the point of firstindex in Julia?
From documentation it says firstindex() finds the first index of a collection. Why not just use 1? What could be the case when it's not 1?
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Determine version of a specific package
How can I get the version number for a specific package?
The obvious way is to get the dictionary with all installed packages, and then filter for the one of interest:
pkgs = Pkg.installed();
pkgs["...
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how to find version number of Julia? Is there a ver() command?
I installed Julia studio 0.4.4, and found it does not support multi-line comments #=...=# so I wanted to find what version of Julia it is running.
In Matlab one types the command ver which not only ...
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Convert float to int in Julia Lang
Is there a way to convert a floating number to int in Julia? I'm trying to convert a floating point number to a fixed precision number with the decimal part represented as 8bit integer. In order to do ...
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Julia (Julia-lang) Performance Compared to Fortran and Python
I adapted a simple program to compute and plot the movement vortices of to Julia to test the language, I also wrote it in Python for no particular reason.
(Disclaimer: 1. Every performance comparison ...
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How to make a GUI in Julia?
I'm new at programming in Julia and I need to create a GUI.
I've been looking for information and I can't find anything useful. I tried to search information in the Julia official web page, but it ...
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How to write "good" Julia code when dealing with multiple types and arrays (multiple dispatch)
OP UPDATE: Note that in the latest version of Julia (v0.5), the idiomatic approach to answering this question is to just define mysquare(x::Number) = x^2. The vectorised case is covered using ...
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What is the difference between @code_native, @code_typed and @code_llvm in Julia?
While going through julia, I wanted to have a functionality similar to python's dis module.
Going through over the net, I found out that the Julia community have worked over this issue and given ...
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Julia DataFrame: remove column by name
The DataFrame type in Julia allows you to access it as an array, so it is possible to remove columns via indexing:
df = df[:,[1:2,4:end]] # remove column 3
The problem with this approach is that I ...
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How does one clear or remove a global in julia?
Is there any syntax that does something similar to MATLAB's "clear" i.e. if I have a global variable "a". How do I get rid of it? How do I do the analog of
clear a
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Does a Python-like virtualenv exist in Julia?
Is there a Python-like virtualenv environment simulator for Julia where one can do development in a local, virtual environment?
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What on earth is an inner constructor?
TL;DR:
what's the accurate definition of inner constructors? In Julia-v0.6+, is it right to say "any constructor that can be called with the signature typename{...}(...)(note the {} part) is an inner ...
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Why is operating on Float64 faster than Float16?
I wonder why operating on Float64 values is faster than operating on Float16:
julia> rnd64 = rand(Float64, 1000);
julia> rnd16 = rand(Float16, 1000);
julia> @benchmark rnd64.^2
...
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Julia: How to copy data to another processor in Julia
How do you move data from one processor to another in julia?
Say I have an array
a = [1:10]
Or some other data structure. What is the proper way to put it on all other available processors so that ...
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Julia: Convert numeric string to float or int
I am trying to write numeric data pulled from a database into a Float64[]. The original data is in ::ASCIIString format, so trying to push it to the array gives the following error:
julia> push!(a,...
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set the random seed in julia generator of random numbers
I would like to do a couple of checkings using the random generator for normal distributed numbers in julia. So what I would like is to obtain the same sequence of pseudo-random numbers.
Actually, I ...
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What is the difference between "==" and "===" comparison operators in Julia?
What is the difference between == and === comparison operators in Julia?
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I have a high-performant function written in Julia, how can I use it from Python?
I have a found a Julia function that nicely does the job I need.
How can I quickly integrate it to be able to call it from Python?
Suppose the function is
f(x,y) = 2x.+y
What is the best and most ...
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How to get fields of a Julia object
Given a Julia object of composite type, how can one determine its fields?
I know one solution if you're working in the REPL: First you figure out the type of the object via a call to typeof, then ...
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Floating point math in different programming languages
I know that floating point math can be ugly at best but I am wondering if somebody can explain the following quirk. In most of the programing languages I tested the addition of 0.4 to 0.2 gave a ...
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How to read a file line by line in Julia?
How do I open a text file and read it line by line? There are two different cases I'm interested in answers for:
Get all the lines in an array at once.
Process each line one at a time.
For the ...
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How do I select a random item from a weighted array in Julia?
Consider two 1-dim arrays, one with items to select from and one containing the probabilities of drawing the item of the other list.
items = ["a", 2, 5, "h", "hello", 3]
weights = [0.1, 0.1, 0.2, 0.2,...
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Converting integer to string in Julia
I want to convert an integer to a string in Julia.
When I try:
a = 9500
b = convert(String,a)
I get the error:
ERROR: LoadError: MethodError: Cannot `convert` an object of type Int64 to an object ...
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