R Programming Questions and Answers – Debugging

This set of R Programming Language Multiple Choice Questions & Answers (MCQs) focuses on “Debugging”.

1. What will be the output of the following R expression?

  > log(-2.3)

a) Warning in log(-2.3): NaNs produced
b) 1
c) Null
d) 0
View Answer

2. Point out the correct statement?
a) Vectorizing the function can be accomplished easily with the Vectorize() function
b) There are different levels of indication that can be used, ranging from mere notification to fatal error
c) Vectorizing the function can be accomplished easily with the vector() function
d) Warnings are generated by the run() function
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3. What will be the value of following R expression?
a) Warning in log(c(-1, 2)): NaNs produced
b) Error in log(c(-1, 2)): NaNs produced
c) Message
d) All of the mentioned
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4. What will be the output of the following R code?

> printmessage2 <- function(x) {
+                      if(is.na(x))
+                              print("x is a missing value!")
+                      else if(x > 0)
+                              print("x is greater than zero")
+                      else
+                              print("x is less than or equal to zero")
+                      invisible(x)
+ }
> printmessage2(NA)

a) “x is a missing value!”
b) “x is greater than zero”
c) “x is less than or equal to zero”
d) Error
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5. What will be the output of the following R code?

> printmessage <- function(x) {
+                      if(x > 0)
+                           print("x is greater than zero")
+                      else
+                           print("x is less than or equal to zero")
+                      invisible(x)
+ }
> printmessage(NA)

a) Error
b) Warning
c) Messages
d) x is greater than zero
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6. What will be the output of the following R code?

> mean(x)
  Error in mean(x) : object 'x' not found
> traceback()

a) 1: mean(x)
b) Null
c) 0
d) 2
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7. The recover() function will first print out the function call stack when an _______ occurs.
a) Error
b) Warning
c) Messages
d) delete
View Answer

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