1. What is an array in R?
a) A data structure for storing tabular data
b) A 1-dimensional list of elements
c) A multi-dimensional data structure
d) A collection of key-value pairs
Answer:
c) A multi-dimensional data structure
Explanation:
An array in R is a multi-dimensional data structure that can store data in more than two dimensions.
2. How do you create a 2×3 array of zeros in R?
a) array(0, dim = c(2, 3))
b) zeros(2, 3)
c) matrix(0, 2, 3)
d) Both a and c
Answer:
d) Both a and c
Explanation:
Both array(0, dim = c(2, 3)) and matrix(0, 2, 3) create a 2×3 array (or matrix) filled with zeros.
3. What is the result of applying the dim() function to an array in R?
a) The number of elements in the array
b) The type of elements in the array
c) The dimensions of the array
d) The sum of the elements in the array
Answer:
c) The dimensions of the array
Explanation:
The dim() function returns the dimensions of an array, such as the number of rows and columns in a 2-dimensional array.
4. How can you access the element in the 2nd row and 3rd column of a 2-dimensional array 'arr' in R?
a) arr[2, 3]
b) arr(2, 3)
c) arr[[2, 3]]
d) arr{2, 3}
Answer:
a) arr[2, 3]
Explanation:
Elements in an array are accessed using the [row, column] indexing in R.
5. How do you create a 3-dimensional array in R?
a) array(data, dim = c(x, y, z))
b) matrix(data, x, y, z)
c) list(data, dim = c(x, y, z))
d) c(data, dim = c(x, y, z))
Answer:
a) array(data, dim = c(x, y, z))
Explanation:
A 3-dimensional array in R is created using the array() function with the 'dim' parameter specifying the dimensions.
6. What does the apply() function do with an array in R?
a) Changes the dimensions of the array
b) Applies a function to the array's elements
c) Converts the array to a vector
d) Creates a transpose of the array
Answer:
b) Applies a function to the array's elements
Explanation:
The apply() function applies a function to the margins of an array or matrix.
7. How do you combine two arrays of the same dimension in R?
a) append()
b) c()
c) merge()
d) array_merge()
Answer:
b) c()
Explanation:
The c() function can be used to combine two or more arrays of the same dimension into a single array in R.
8. Which function can be used to transpose a 2-dimensional array in R?
a) transpose()
b) swap()
c) t()
d) flip()
Answer:
c) t()
Explanation:
The t() function is used to transpose a 2-dimensional array or matrix in R.
9. How do you initialize an array with specific dimensions but without data in R?
a) array(dim = c(x, y, z))
b) empty_array(x, y, z)
c) array(NULL, dim = c(x, y, z))
d) matrix(dim = c(x, y, z))
Answer:
a) array(dim = c(x, y, z))
Explanation:
The array() function can be used to create an array with specific dimensions but without initializing the data.
10. What is the use of the aperm() function with an array in R?
a) To append elements to the array
b) To change the order of array dimensions
c) To apply a function to each element
d) To aggregate array data
Answer:
b) To change the order of array dimensions
Explanation:
The aperm() function is used to permute or rearrange the dimensions of an array.
11. Can you store different data types in a single array in R?
a) Yes, arrays can store mixed data types
b) No, arrays must contain elements of the same type
c) Yes, but only if the array has more than two dimensions
d) No, it requires a special kind of array
Answer:
b) No, arrays must contain elements of the same type
Explanation:
Arrays in R are homogeneous and can only store elements of the same data type.
12. How do you create a 2x2x2 array filled with random numbers in R?
a) array(runif(8), dim = c(2, 2, 2))
b) random(2, 2, 2)
c) matrix(runif(8), 2, 2, 2)
d) list(runif(8), dim = c(2, 2, 2))
Answer:
a) array(runif(8), dim = c(2, 2, 2))
Explanation:
The array() function combined with runif(8) (which generates 8 random numbers) can be used to create a 2x2x2 array filled with random numbers.
13. What does the expression arr[,,1] represent for a 3-dimensional array 'arr' in R?
a) The first row of the array
b) The first column of the array
c) The first element of the array
d) The first matrix slice of the array
Answer:
d) The first matrix slice of the array
Explanation:
In a 3-dimensional array, arr[,,1] represents the first matrix slice along the third dimension.
14. How do you determine if an object is an array in R?
a) is.array(object)
b) typeof(object)
c) is.type(array)
d) object.type()
Answer:
a) is.array(object)
Explanation:
The is.array() function is used to check if an object is an array in R.
15. How do you create an array from a vector in R?
a) Using the vector() function with dimensions
b) Using the array() function with the vector and dimensions
c) Directly converting the vector to an array
d) Arrays cannot be created from vectors
Answer:
b) Using the array() function with the vector and dimensions
Explanation:
To create an array from a vector, use the array() function and specify the vector and the desired dimensions.