The Brass Tacks of Julia Programming – Part III

See Part I for instructions on basic arithmetic operations and Part II for working with matrices

Using R and Python code in Julia

There can be times where you want to use your R or Python code as the libraries to perform certain operations may not be available in Julia.

However, using 2 languages to perform a certain operation can be a challenge. Hence, Julia provides an option to use R and Python code by using the “PyCall” and “RCall” packages.

How to use Python code in Julia

Here’s how you can use your Python code in Julia.

# Install the "PyCall" package for Python
using Pkg
Pkg.add("PyCall")
using PyCall

## Importing numpy package from Python
np = pyimport("numpy")

## Using numpy package in Julia
np.array([1,2,3])

Output:

3-element Vector{Int64}:
1
2
3

How to use R code in Julia

Let’s look at an example of using R in Julia.

# Install "RCall" package for R
Pkg.add("RCall")
using RCall

# There are several ways to call R code

# Method 1
# Calling the mean() function from R
rcall(:mean, [1,2,3])

# Method 2 for user-defined functions
R"""
power_4 <- function(x)
{
return(x^4)
}"""
    
## Calling the defined function
rcall(:power_4, 5)

Output:

RObject{RealSxp}
[1] 2
RObject{RealSxp}
[1] 625

For further details on using the RCall package, you can refer here.

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Python vs Julia – Comparison of syntax for basic operations

Feature	Python	Julia
Column vector	[1, 2, 3]	[1,2,3]
Row vector	[[1], [2], [3]]	[1 2 3]
Sequence of numbers	range(1, 10,2)	[1:2:10; ]
Matrix	[[1,2] , [3,4]]	[1 2; 3 4]
Random numbers	np.random.rand(4,5)	rand(4,5)
Mutation	inplace =True	!
Matrix to vector	A.flatten()	A[:]
Conjugate of a matrix	A.conj()	A’
Element wise operation	map()	.
Power	var**2	var^2
Indexing	Starts from 0	Starts from 1
Maximum value	max(A)	maximum(A)
Minimum value	min(A)	minimum(A)
For loop	for i in range(n): # command	for i in 1:n # command end
While loop	While i <=n:	While i <=n
If-else	If i <=m: # command Else: #command	if i <=m # command else # command end
Temporary function	Y = lambda x: x**5	Y = x -> x^5
Function	def func(y, x): return y + 3*x	func(y, x) = y + 3x OR function func(y, x) return y + 3x end

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