Question
R PROGRAMMING . Consider the following code, where the operations in the braced area of the while loop have been omitted: mystring
R PROGRAMMING
. Consider the following code, where the operations in the braced area of the while loop have been omitted:
mystring <- "R fever"
index <- 1
ecount <- 0
result <- mystring
while(ecount<2 && index<=nchar(mystring)){ # several omitted operations # }
result
Your task is to complete the code in the braced area so it inspects mystring character by character until it reaches the second instance of the letter e or the end of the string, whichever comes first. The result object should be the entire character string if there is no second e or the character string made up of all the characters up to, but not including, the second e if there is one. For example, mystring <- "R fever" should provide result as "R fev". This must be achieved by following these operations in the braces:
1. Use substr (Section 4.2.4) to extract the single character of mystring at position index.
2. Use a check for equality to determine whether this singlecharacter string is either "e" OR "E". If so, increase ecount by 1.
3. Next, perform a separate check to see whether ecount is equal to 2. If so, use substr to set result equal to the characters between 1 and index-1 inclusive.
4. Increment index by 1.
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