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A nested for loop in R is used when we want to iterate through multiple dimensions, such as rows and columns of a matrix, or for creating patterns. we will discuss how to print multiplication tables up to a certain number with its working example in the R Programming Language using R for loop conditions. Everyone found an easy way for pattern printing in other programming languages. But it’s a tough task using the R language
Approach:
- Start the first loop for the number of lines
- Start the second loop for the item to be displayed
- Print item
- Increment the second loop until a condition is reached
- Increment the first loop until the condition is true
- Continue in this fashion
Syntax:
for (i in 1:n) {
for (j in 1:m) {
# Pattern generation logic
}
}
Example 1: Printing a right-angle triangle
R
n <- 5
for (i in 1:n) {
for (j in 1:i) {
cat("* ")
}
cat("\n")
}
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Output:
*
* *
* * *
* * * *
* * * * *
- Initialize n=5, indicating the number of rows in the pattern.
- The outer loop iterates over the range of i from 1 to n (inclusive), controlling the number of rows in the pattern.
- Inside the outer loop, the inner loop iterates over the range of j from 1 to the value of i (inclusive). This loop controls the number of asterisks to be printed in each row.
- Inside the inner loop, cat(“* “) prints an asterisk followed by a space, generating the pattern elements.
- After the inner loop, cat(“\n”) is used to print a newline character, moving to the next line after printing the pattern for each row.
Example 2: Printing a rectangular pattern
R
n <- 4
m <- 6
for (i in 1:n) {
for (j in 1:m) {
cat("* ")
}
cat("\n")
}
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Output:
* * * * * *
* * * * * *
* * * * * *
* * * * * *
- Initialize n=4, indicating the number of rows in the pattern.
- The outer loop iterates over the range of i from 1 to n (inclusive), controlling the number of rows in the pattern.
- Inside the outer loop, the inner loop iterates over the range of j from 1 to the value of i (inclusive). This loop controls the number of asterisks to be printed in each row.
- Inside the inner loop, cat(“* “) prints an asterisk followed by a space, generating the pattern elements.
- After the inner loop, cat(“\n”) is used to print a newline character, moving to the next line after printing the pattern for each row.
Example 3: Draw inverted triangle
R
star = c()
i=1
j=5
while(i<=5){
for(j in 1:j){
star = c(star, "*")
}
print(star)
star = c()
i=i+1
j=j-1
}
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Output:
[1] "*" "*" "*" "*" "*"
[1] "*" "*" "*" "*"
[1] "*" "*" "*"
[1] "*" "*"
[1] "*"
star = c(): Initializes an empty vector star to store the stars for each row.i = 1: Initializes the row counter to 1.j = 5: Initializes the column counter to 5 (this represents the number of stars in the first row).while (i <= 5) { ... }: This is the outer while loop that iterates through 5 rows.for (j in 1:j) { ... }: This is the inner for loop that iterates through the stars within a row. star = c(star, "*"): Adds a star to the current row.star = c(): Clears the star vector to prepare for the next row.i = i + 1: Increments the row counter for the next iteration.j = j - 1: Reduce the number of stars for the next row.
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