R (Programming Language) Part-I

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Which is not a property of lists and vectors? *

1 point

type

length

attributes

scalar

In the image below, the data frame is named rates. The statement sd(rates[, 2]) returns 39. As what does R regard Ellen's product ratings? *

1 point

sample with replacement

population

trimmed sample

sample <-- not sure

What is the principal difference between an array and a matrix? *

1 point

A matrix has two dimensions, while an array can have three or more dimensions.

An array is a subtype of the data frame, while a matrix is a separate type entirely.

A matrix can have columns of different lengths, but an array's columns must all be the same length.

A matrix may contain numeric values only, while an array can mix different types of values.

The variable height is a numeric vector in the code below. Which statement returns the value 35? *

1 point

height(length(height))

height[length(height)]

height[length[height]]

height(5)

Which choice does R regard as an acceptable name for a variable? *

1 point

Var_A!

\_VarA

.2Var_A

Var2_A

Two variable in the mydata data frame are named Var1 and Var2. How do you tell a bivariate function, such as cor.test, which two variables you want to analyze? *

1 point

cor.test(Var1 ~ Var2)

cor.test(mydata$(Var1,Var2))

cor.test(mydata$Var1,mydata$Var2)

cor.test(Var1,Var2, mydata)

What is the value of y in this code? *

1 point

Inf

Null

NaN

d.pizza is a data frame. It's a column named temperature contains only numbers. If you extract temperature using the [] accessors, its class defaults to numeric. How can you access temperature so that it retains the class of data.frame? *

1 point

class( d.pizza( , "temperature" ) )

class( d.pizza[ , "temperature" ] )

class( d.pizza$temperature )

class( d.pizza[ , "temperature", drop=F ] )

What do you use to take an object such as a data frame out of the workspace? *

1 point

remove()

erase()

detach()

delete()

How to name rows and columns in DataFrames and Matrices F in R? *

1 point

data frame: names() and rownames() matrix: colnames() and row.names()

data frame: names() and row.names() matrix: dimnames() (not sure)

data frame: colnames() and row.names() matrix: names() and rownames()

data frame: colnames() and rownames() matrix: names() and row.names()

How does a vector differ from a list? *

1 point

Vectors are used only for numeric data, while lists are useful for both numeric and string data.

Vectors and lists are the same thing and can be used interchangeably.

A vector contains items of a single data type, while a list can contain items of different data types.

Vectors are like arrays, while lists are like data frames.

Ournames is a character vector. What values does the statement below return to Cpeople? *

1 point

records where the first character is a C

any record with a value containing a C

TRUE or FALSE, depending on whether any character in ournames is C

TRUE and FALSE values, depending on whether the first character in an ournames record is C

What is mydf$y in this code? *

1 point

list

string

factor

character vector

What value does this statement return? *

1 point

365

What statement shows the objects on your workspace? *

1 point

list.objects()

print.objects()

getws()

ls()

You accidentally display a large data frame on the R console, losing all the statements you entered during the current session. What is the best way to get the prior 25 statements back? *

1 point

console(-25)

console(reverse=TRUE)

history()

history(max.show = 25)

A data frame named d.pizza is part of the DescTools package. A statement is missing from the following R code and an error is therefore likely to occur. Which statement is missing? *

1 point

attach(d.pizza)

summarize(deliver)

mean <- rbind(d.pizza,count)

deliver[!complete.cases(deliver),]

Review the following code. What is the result of line 3? *

1 point

[1] 1 2 3

[1] "1" 2 "3"

[1] "1" "2" "3"

[1] 7 9

Which function displays the first five rows of the data frame named pizza? *

1 point

BOF(pizza, 5)

first(pizza, 5)

top(pizza, 5)

head(pizza, 5)

In the image below, the data frame on lines 1 through 4 is named StDf. State and Capital are both factors. Which statement returns the results shown on lines 6 and 7? *

1 point

StDf[1:2,-3]

StDf[1:2,1]

StDf[1:2,]

StDf[1,2,]

Review the statements below. Does the use of the dim function change the class of y, and if so what is y's new class? *

1 point

No, y's new class is "array".

Yes, y's new class is "matrix".

No, y's new class is "vector".

Yes, y's new class is "integer".

How does a matrix differ from a data frame? *

1 point

A matrix may contain numeric values only.

A matrix must not be singular.

A data frame may contain variables that have different modes.

A data frame may contain variables of different lengths.

Review line 1 below. What does the statement in line 2 return? *

1 point

[1] 1 2 4 5

"C"

[1] "1" "2" "C" "4" "5"

[1] 1 2 C 4 5

What function joins two or more column vectors to form a data frame? *

1 point

rbind()

cbind()

bind()

coerce()

What does c contain? *

1 point

[1] NaN

[1] -4

[1] 4 -1 -1 2

TRUE FALSE FALSE TRUE

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