Chap 3 Review

\[ \newcommand{\dnorm}{\text{dnorm}} \newcommand{\pnorm}{\text{pnorm}} \newcommand{\recip}{\text{recip}} \]

Exercise 1  

1. Is xx a legitimate name in R?

Yes       No      

question id: 03-legitimate-name-1

2. Is x_x a legitimate name in R?

Yes       No      

question id: 03-legitimate-name-2

3. Is -x a legitimate name in R?

Yes       No      

question id: 03-legitimate-name-3

4. Is 3x a legitimate name in R?

True       No      

question id: 03-legitimate-name-4

5. Is sqrt a legitimate name in R?

Yes       No      

question id: 03-legitimate-name-5

6. Is x + y a legitimate name in R?

True       No      

question id: 03-legitimate-name-6

7. Is 3 * x a legitimate name in R?

True       No      

question id: 03-legitimate-name-7

8. Is xprime a legitimate name in R?

Yes       No      

question id: 03-legitimate-name-8

9, Is x prime a legitimate name in R?

Yes       No      

question id: 03-legitimate-name-9

10. Is dx a legitimate name in R?

Yes       No      

question id: 03-legitimate-name-10

11. Is dx_f a legitimate name in R?

Yes       No      

question id: 03-legitimate-name-11

Exercise 2  

1. What’s wrong with this assignment statement? x < 4

Nothing

it is missing part of the <- token.

x is an improper name.

question id: 03-whats-wrong-1

2. What’s wrong with this assignment statement? 3*x <- 4

Nothing

It should use addition instead of multiplication.

The item to the left of <- needs to be a name

There is no x on the right-hand side of the assignment arrow.

question id: 03-whats-wrong-2

3. What’s wrong with this assignment statement? x -> 3+4

Nothing

You cannot use addition in an assignment statement.

The assignment arrow has to point toward the name, not the value

question id: 03-whats-wrong-3

Exercise 3 We can write something like \[f(x) \equiv x^2\] in mathematical notation. Is it legit in R to write f(x) <- x^2 ?

Yes, it is fine.

f(x) is not a valid name in R.

Almost. You need to use ≈ instead of <- .

question id: IK57Kb

Exercise 4 Which of these is the right way to translate \(e^x\) into R?

e^x

exp(x)

e(x)

There is no R equivalent.

question id: cbynFm

Exercise 5 If x has been assigned the value pi/2, what will be the value of the R expression 2 sin(x)?

0, since \(\sin(\pi/2) = 0\).

1, since \(\sin(\pi/2) = 1\).

2, since \(\sin(\pi/2) = 1\).

No value. The expression is in error.

question id: 2yXUur

Exercise 6  

1. What’s wrong with the R command

f <- 3*x + 2

for defining a function?

It needs to be f(x) <- 3*x + 2

It needs to be f <- makeFun(3*x + 2)

It needs to be f <- makeFun(3*x + 2 ~ x).

Nothing is wrong

question id: bad-expressions-1

2. What’s wrong with this R command for creating an exponential function named g?

g <- makeFun(e^y ~ y)

e^y is not the exponential function

It uses y as the argument instead of x.

Better to name the argument x

Nothing

question id: bad-expressions-2

3. What’s suspect about this R command?

g <- makeFun(exp(y) ~ x)

The formula is exp(y) but the argument name is x

There is a tilde expression as the argument to makeFun().

The function name should be G, not g.

Nothing

question id: bad-expressions-3

4. What’s wrong with the R expression sin*(x + 3)?

There is no function named sin*()

It should be sin+(x+3)

It should be sin^(x+3)

Nothing

question id: bad-expressions-4

Exercise 7 What does e^3 mean in R?

It corresponds to \(e^3\), which happens to be 20.09

A shorthand for eee.

The value stored under the name e will be raised to the third power.

question id: Eb8Pqe

Exercise 8 What’s missing in the R expression (x+3)(x+1)?

There is a missing closing parenthesis.

There is an extra closing parenthesis.

The multiplication symbol, *, is missing.

Nothing

question id: QEt5un

Exercise 9 Which of these phrases is most appropriate for describing what the R command z <- sin(17) is doing?

Applies a function to an input to produce an output that will be stored under a name.

Applies a function to an input to produce an output.

Makes a copy of an existing object.

The name of an object.

it is invalid as a command.

question id: WWacOx

Exercise 10 Which of these phrases is most appropriate for describing what the R command sin(17) is doing?

Gives a name to a value.

Applies a function to an input to produce an output.

Makes a copy of an existing object.

The name of an object.

It is invalid as a command.

question id: KdtU01

Exercise 11 Which of these phrases is most appropriate for describing what the R command z <- x is doing?

Gives a name to a value.

Applies a function to an input to produce an output.

Makes a copy of an existing object.

The name of an object.

It is invalid as a command.

question id: 4vzqOX

Exercise 12 Which of these phrases is most appropriate for describing what the R command fred is doing?

Gives a name to a value.

Applies a function to an input to produce an output.

Makes a copy of an existing object.

Produces the value stored under the name fred.

It is invalid as a command.

question id: jW85Kl

Exercise 13 In the following statement, what is pnorm?

pnorm(3, mean=4, sd=6 )

The name of the function being applied to the three arguments.

A named argument

An argument to be used without a name.

question id: IEokf0

Exercise 14 In the following statement, what is mean=4?

pnorm(3, mean=4, sd=6 )

The name of the function being applied to the three arguments.

A named argument

An argument whose meaning is set by position within the parentheses.

question id: VxuzVl

Exercise 15 In the following statement, what is 3?

pnorm(3, mean=4, sd=6 )

The name of the function being applied to the three arguments.

A named argument

An argument whose meaning is set by position within the parentheses.

question id: oBHViq

Exercise 16 Will these two statements give the same result?

pnorm(y = 3, mean = 4, sd = 6)

pnorm(3, mean = 4, sd = 6)

If you’re not sure, try running the two statements.

Yes, same arguments to the same function means the output will be the same.

No, but you would only learn why from the error message produced when you execute the command. As it happens, the name of the first argument to pnorm() is q. Trying to call it y will not work.]

question id: Nxcaf8

Exercise 17 Will these two statements give the same result?

pnorm(3, mean=4, sd=6)

pnorm(3, sd=6, mean=4)

Yes.       No. The arguments are different.      

question id: uOuqB7

Exercise 18 Will these two statements give the same result?

pnorm(3, mean=4, sd=6)

pnorm(3, sd=4, mean=6)

Yes       No      

question id: oxpoxr

Exercise 19 What is the value of 16^1/2?

4       8      

question id: 73iI9q

Exercise 20 Suppose n <- 3. What will be the value of 2^n-1?

4       7       8      

question id: kexahG

Exercise 21 Suppose n <- 3. What will be the value of 2^(n-1)?

4       7       8      

question id: LZcAvO

Exercise 22 In g <- makeFun(3*z + 2 ~ z), which is the name of the input to the function g()?

\(x\)       \(y\)       \(z\)       \(t\)      

question id: Xv9nXx

Exercise 23 Will this statement work in R? sin(4)

Yes       No      

question id: IayXv5

Exercise 24 Will this statement work in R? Sin(4)

Yes       No      

question id: M5Fu3U

Exercise 25 Will this statement work in R to calculate \(\sin(4)\)? sin[4]

Yes       No      

question id: PYGaqQ

03-review.rmarkdown

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