▸ R (Programming Language) | LinkedIn Skill Assessment Quiz Solutions
Recommended R Programming Courses:
- Udemy: R Programming - R Language for Absolute Beginners
- Udemy: R Programming A-Z™: R For Data Science With Real Exercises!
- Udemy: R Programming: Advanced Analytics In R For Data Science
- Coursera: Data Science: Foundations using R Specialization
- Coursera: Statistics with R Specialization
- LinkedIn: Master R for Data Science
- edX: R Programming Fundamentals
- edureka: Data Analytics with R Certification Training
- Eduonix: R Programming for Beginners
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How does a matrix differ from a data frame?
- 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.
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What value does this statement return?
unclass(as.Date("1971-01-01"))- 1
- 365
- 4
- 12
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What do you use to take an object such as a data frame out of the workspace?
- remove()
- erase()
- detach()
- delete()
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Review the following code. What is the result of line 3?
xvect<-c(1,2,3) xvect[2] <- "2" xvect- [1] 1 2 3
- [1] “1” 2 “3”
- [1] “1” “2” "3"
- [1] 7 9
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The variable height is a numeric vector in the code below. Which statement returns the value 35?
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height(length(height)) -
height[length(height)] -
height[length[height]] -
height(5)
-
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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?
- sample with replacement
- population
- trimmed sample
- sample <-- not sure
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Which choice does R regard as an acceptable name for a variable?
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Var_A! -
\_VarA -
.2Var_A -
Var2_A
-
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What is the principal difference between an array and a matrix?
- 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.
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Which is not a property of lists and vectors?
- type
- length
- attributes
- scalar
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In the image below, the data frame on lines 1 through 4 is names StDf. State and Capital are both factors. Which statement returns the results shown on lines 6 and 7?
- StDf[1:2,-3]
- StDf[1:2,1]
- StDf[1:2,]
- StDf[1,2,]
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Which function displays the first five rows of the data frame named pizza?
- BOF(pizza, 5)
- first(pizza, 5)
- top(pizza, 5)
- head(pizza, 5)
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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?
- console(-25)
- console(reverse=TRUE)
- history()
- history(max.show = 25)
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d.pizza is a data frame. It’s column named temperature contains only numbers. If u extract temperature using the [] accessors, its class defaults to numeric. How can you access temperature so that it retains the class of data.frame?
> class( d.pizza[ , "temperature" ] ) > "numeric"-
class( d.pizza( , "temperature" ) ) -
class( d.pizza[ , "temperature" ] ) -
class( d.pizza$temperature ) -
class( d.pizza[ , "temperature", drop=F ] )
-
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What does c contain?
a <- c(3,3,6.5,8) b <- c(7,2,5.5,10) c <- a < b- [1] NaN
- [1] -4
- [1] 4 -1 -1 2
- [1] TRUE FALSE FALSE TRUE
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Review the statements below. Does the use of the dim function change the class of y, and if so what is y’s new class?
> y <- 1:9 > dim(y) <- c(3,3)- No, y’s new class is “array”.
- Yes, y’s new class is “matrix”.
- No, y’s new class is “vector”.
- Yes, y’s new class is “integer”.
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What is
mydf$yin this code?
mydf <- data.frame(x=1:3, y=c("a","b","c"), stringAsFactors=FALSE)- list
- string
- factor
- character vector
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How does a vector differ from a list?
- Vectors are used only for numeric data, while list 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.
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What statement shows the objects on your workspace?
- list.objects()
- print.objects()
- getws()
- ls()
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What function joins two or more column vectors to form a data frame?
- rbind()
- cbind()
- bind()
- coerce()
-
Review line 1 below. What does the statement in line 2 return?
1 mylist <- list(1,2,"C",4,5) 2 unlist(mylist)- [1] 1 2 4 5
- “C”
- [1] “1” “2” “C” “4” "5"
- [1] 1 2 C 4 5
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What is the value of y in this code?
x <- NA y <- x/1- Inf
- Null
- NaN
- NA
-
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?
-
cor.test(Var1 ~ Var2) -
cor.test(mydata$(Var1,Var2)) -
cor.test(mydata$Var1,mydata$Var2) -
cor.test(Var1,Var2, mydata)
-
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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?
library(DescTools) deliver <- aggregate(count,by=list(area,driver), FUN=mean) print(deliver)-
attach(d.pizza) -
summarize(deliver) -
mean <- rbind(d.pizza,count) -
deliver[!complete.cases(deliver),]
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How to name rows and columns in DataFrames and Matrices F in R?
- 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()
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Which set of two statements-followed by the cbind() function-results in a data frame named vbound?
-
A
v1<-list(1,2,3) v2<-list(c(4,5,6)) vbound<-cbind(v1,v2) -
B
v1<-c(1,2,3) v2<-list(4,5,6)) vbound<-cbind(v1,v2) -
C
v1<-c(1,2,3) v2<-c(4,5,6)) vbound<-cbind(v1,v2)
-
-
ournames is a character vector. What values does the statement below return to Cpeople?
Cpeople <- ournames %in% grep("^C", ournames, value=TRUE)
- 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 or FALSE values, depending on whether the first character in an ournames record is C
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What is the value of names(v[4])?
v <- 1:3 names(v) <- c("a", "b", "c") v[4] <- 4- ""
- d
- NULL
- NA
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Which of the following statements doesn’t yield the code output below. Review the following code. What is the result of line 3?
x <- c(1, 2, 3, 4) Output: [1] 2 3 4- x[c(2, 3, 4)]
- x[-1]
- x[c(-1, 0, 0, 0)]
- x[c(-1, 2, 3, 4)]
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Given DFMerged <- merge(DF1, DF2) and the image below, how manu rows are in DFMerged?
DF1(data frame 1): DF2(data frame 2): VarA VarB VarA VarD 1 1 2 1 18 21 2 4 5 2 19 22 3 7 8 3 20 23- 6
- 9
- 3
- 0
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