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How to Fix: incorrect number of subscripts on matrix in R

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  • Last Updated : 21 Feb, 2022

Getting errors in programming is quite common and their frequency increase when our source code becomes bulkier. In this article, we are going to discuss how to fix: the incorrect number of subscripts on the matrix in R. 

This error doesn’t give us any clue at the first appearance. This error may occur due to a very small mistake. This error may be easy for programmers to make but finding this error sometimes becomes challenging for most of the programmers. 

When this error might occur?

These errors might occur when the programmer tries to use matrix notation on a data structure that is not a matrix on its own. This type of mistake is a normal one but sometimes it might be difficult to find if you don’t have any clarity regarding the data structure being used. 

Example: 

R




# R program to illustrate when this 
# error might occur
  
# Creating a vector
vect = rep(1, 5)
  
# Assign values in the created vector 
for(i in 1:5)
{
  # Assigning at all columns of the 
  # ith row
  vect[i,] = 10
}


Output:

Why this error might occur?

This type of error occurs when the programmer tries to apply matrix notation to a vector. 

Example:

In the below source code, we have created a vector vect (1 – dimensional data structure). Using a for-loop we are iterating from i = 1 to i = 100 and at each step of the iteration, we are assigning the value 10 to all columns of the ith row. But vect is a 1-dimensional data structure and we are applying matrix notation on it. Hence, the below source code will lead to an error: “the incorrect number of subscripts on the matrix” as clearly seen in the output.

R




# R program to illustrate reasons for the error
  
# Creating a vector
vect = rep(1, 5)
  
# Assign values in the created vector 
for(i in 1:5)
{
  # Assigning at all columns of the ith row
  vect[i,] = 10
}


How to fix this error?

Fixing this error is based upon two different ideologies that are discussed below.

Ideology 1: When we want to deal with the 1-dimensional data structure.

When we are sure that we are going to deal with a 1-dimensional data structure (like a vector) then we can fix this error like the below example.

Example:

R




# R program to fix the error
  
# Creating a vector
vect = rep(1, 5)
  
# Assign values in the created vector 
# Note that we have removed the comma (,)
# Since we are dealing with 1-dimensional 
# data structure
for(i in 1:5)
{
  # Assigning 10 as the value
  # at the ith index of the vect 
  vect[i] = 10
}


Output:

Ideology 2: When we want to deal with the 2-dimensional data structure.

When we are sure that we are going to deal with a 2-dimensional data structure (like a matrix) then we can fix this error like the below example.

Example:

R




# R program to fix the error
  
# Creating a 2-dimensional data structure (matrix)
# mat has 5 rows and 5 columns 
mat = matrix(rep(0,5), nrow=5, ncol=5)
  
# Assign values in the created matrix
# Note that we have added the comma (,)
# Since we are dealing with 2-dimensional
# data structure
for(i in 1:5)
{
  # Assigning 10 as the value
  # at all columns of the ith row  
  mat[i,] = 10
}
  
# Print the matrix
print(mat)


Output:


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