R Programming Questions and Answers – Commands – 3

This set of tough R Programming questions and answers focuses on “Commands – 3”.

1. Which of the following will reverse the order of values in x?
a) rev(x)
b) max(x, na.rm=TRUE)
c) all(x)
d) x%in%y
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2. Which of the following finds row sums for each level of a grouping variable?
a) rowSums (x, na.rm = FALSE, dims = 1)
b) colMeans(x, na.rm = FALSE, dims = 1)
c) rowMeans(x, na.rm = FALSE, dims = 1)
d) rowsum(x, group, reorder = TRUE, …)
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3. Which of the following statement applies the function (FUN) to either rows (1) or columns (2) on object X?
a) apply(x,1,min)
b) apply(x,2,max)
c) col.max(x)
d) apply(X, MARGIN, FUN, …)
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4. Which of the following statement finds the maximum for each column?
a) apply(x,2,max)
b) col.max(x)
c) which.min(x)
d) which.max(x)
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5. which of the following statement tells the row with the minimum value for every column?
a) which.min(x)
b) which.max(x)
c) z=apply(x,1,which.min)
d) z=apply(1,1,which.max)
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6. Which of the following may be used for linear regression?
a) X %*% Y
b) solve(A)
c) solve(A,B)
d) X $*$ Y
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7. Which of the following finds row sums for each level of a grouping variable?
a) as.numeric(x)
b) rowsum(x, group, reorder = TRUE, …)
c) as.order(x)
d) colSums (x, na.rm = FALSE, dims = 1)
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8. Which of the following sets the size of the outer margins for the graph?
a) par(mfrow=c(nrow,mcol))
b) par(ask=TRUE)
c) par(omi=c(0,0,1,0) )
d) par(ask=False)
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9. Which of the following function is used for plotting histogram?
a) hist()
b) histog()
c) histg()
d) histo()
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10. Which of the following will add the title “R language” to the graph?
a) titleAdd( “R language”)
b) title( “R language”)
c) titleBar( “R language”)
d) var(x, na.rm=TRUE)
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