Stats 20 Midterm 1 Practice Questions Spring 2021
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Stats 20 Midterm 1 Practice Questions
Spring 2021
1: my_mean
The sample mean for a sample of values x = x1 , x2 , . . . , xn is defined as
n
i=1
Write a function called my maanu( that computes the mean of a numeric vector x of data values without using the maanu( function. Include an optional logical na -rm argument with a default value of FALsE that specifies whether to remove NA values from the computation.
2: Incorrect my_sign
Observe the following function:
my shfn o, functionux( (
if ux 之 .( (
_poshthva _
)
if ux o .( (
_nafathva _
)
if ux == .( (
_zaro_
)
)
(a)
What is the intended purpose of my shfnu(? For what inputs x will there be no output of my shfnu(?
(b)
Keeping the overall he statement structure (no additional if/else statements), edit my shfnu( so that it works as intended.
(c)
Give example inputs that would cause my shfnu( to throw:
● an error
● one or more warnings
(d)
Using the fixed my shfnu( function from (b), with a single command (e.g. one line of code), produce the output cu _poshthva _ ) _nafathva _ ) _zaro_(
3: my_cumfun
Write a function called my cumeunu( that computes the cumulative eun of a numeric vector x. The out- put of my cumeunux) sum() my cumeunux) prod() my cumeunux) max() my cumeunux) mhn( should be identical to the output of cumsumux() cumprodux() cummaxux() cummhnux( respectively.
4: is.mode
hs -lofhcalu( returns TRuE if the storage mode of the input x is logical and FALsE otherwise. hs -numarhcu( and hs -cgaractaru( work similarly. Write a function called hs -modau( which takes as inputs x: an object, and moda: a length 1 character vector. The output of hs -modaux) moda( should be TRuE only if x has storage mode equal to the moda argument.
NОte : each part would be considered “one” question on the exam. So question 2 is really four questions.
2022-07-09