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Notice that the separator between folders is forward slash (/), as it is onLinux and Mac systems. If you use the Windows operating system, the forwardslash will look odd, because you’re familiar with the backslash (\) of Windowsfolders. When working in Windows, you need to either use the forward slash orescape your backslashes using a double backslash (\\). Compare the followingcode:> setwd(“F:\\git\\stringr”)> getwd()[1] “F:/git/stringr”R will always print the results using /, but you’re free to use either / or \\ asyou please.To avoid having to deal with escaping backslashes in file paths, you can usethe file.path() function to construct file paths that are correct, independentof the operating system you work on. This function is a little bit similar topaste in the sense that it will append character strings, except that theseparator is always correct, regardless of the settings in your operatingsystem:> file.path(“f:”, “git”, “surveyor”)[1] “f:/git/surveyor”It’s often convenient to use file.path() in setting the working directory. Thisallows you specify a cascade of drive letters and folder names, and file.path()then assembles these into a proper file path, with the correct separator character:> setwd(file.path(“F:”, “git”, “roxygen2”))> getwd()[1] “F:/git/roxygen2”You also can use file.path() to specify file paths that include the filenameat the end. Simply add the filename to the path argument. For example, here’sthe file path to the README.md file in the roxygen2 package installed in a localfolder:> file.path(“F:”, “git”, “roxygen2”, “roxygen2”, “README.md” )
[1] “F:/git/roxygen2/roxygen2/README.md”Manipulating filesOccasionally, you may want to write a script that will traverse a given folderand perform actions on all the files or a subset of files in that folder.To get a list of files in a specific folder, use list.files() or dir(). These twofunctions do exactly the same thing, but for backward-compatibility reasons, thesame function has two names:> list.files(file.path(“F:”, “git”, “roxygen2”))[1] “roxygen2” “roxygen2.Rcheck”[3] “roxygen2_2.0.tar.gz” “roxygen2_2.1.tar.gz”Table 12-2 lists some other useful functions for working with files.Table 12-2 Useful Functions for Manipulating FilesFunctionDescription
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Running code without a compilerChap
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Creating errorsCreating warningsRec
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Analyzing tablesExtracting test res
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Working with Pivot TablesUsing the
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R For Dummies ®Published byJohn Wi
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About the AuthorsAndrie de Vries: A
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my choices. Professor Bruce Hardie
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IntroductionWelcome to R For Dummie
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: The prompt symbol, >, is not part
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You want to explore new stuff. You
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Icons Used in This BookAs you read
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Chapter 1Introducing R: The Big Pic
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eferred to as “free as in beer.
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you how to move data and graphics b
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If you have experience in other lan
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variables, get to look at the built
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Below all this information is the R
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that we use it to illustrate the ex
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Starting Your First R SessionIf you
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Using R as a calculator is very int
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Sourcing a ScriptUntil now, you’v
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Finding help on functionsWe discuss
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languages, the backslash character
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Vectorizing your functionsVectorize
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print()R tells you that it needs th
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extensions that much. But using .Rh
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Choosing a clear nameWhen Joris was
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opinions, so the naming of function
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Often, you want to add a bit of ext
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all of them at the beginning of eac
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Part IIGetting Down to Work in RIn
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calculator.Vector operations: Vecto
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Suppose that Granny and Geraldine d
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FunctionWhat It Doesabs(x)log(x,bas
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decision to use scientific notation
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operations in Chapter 7.Actually, o
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NaN in calculations. The outcome of
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Take a look at the vector baskets.o
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way the value is stored in memory.R
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[1] 12 4 4 6 9 3 5 3 2 2 12 9The re
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Okay, this example isn’t too impr
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R doesn’t have an Undo button, so
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x < yx baskets.of.Granny > 5[1] TR
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that value (refer to “Dealing wit
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all(). To find out whether Granny w
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You can tell quite a few things abo
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third game, and so on.The vector re
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1st 2nd 3rd 4th 5th 6th-67 25 20 50
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In this section, you take a look at
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LETTERS[24:26][1] “X” “Y”
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Creating and assigning named vector
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Similar to the way that R displays
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[1] “The quick brown FOX jumps ov
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R performs lexicographic sorting, a
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The result of grep() is a numeric v
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Suppose you have the sentence He is
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Regular expressions allow three way
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lexicographically sorted, unique va
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difference between the levels and t
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vector subsisting rules. For exampl
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table(state.region)state.regionNort
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Chapter 6Going on a Date with RIn T
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startDate xm xm[1] “2012-01-01
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Table 6-2 Some Format Codes for Dat
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As you can see, as.POSIXct() takes
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Formatting Dates and TimesTo format
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Now you know the exact time when we
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project.org/web/packages/lubridate/
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They contain only a single type of
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To get only the number of rows, you
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[1,] 1 4 7 10[2,] 2 5 8 11[3,] 3 6
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id first.matrix[-id][1] 1 2 3 4 5
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[2,] 2 5 8 11[3,] 3 4 9 12You also
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the way. You can try that out yours
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constructing a matrix second.matrix
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[2,] 4 5 6[3,] 7 8 9[4,] 10 11 12Yo
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Using the creator functionsYou can
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[2,] 5 17[3,] 8 20[4,] 11 23This re
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[1] 6Likewise, the ncol() function
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data frame with character vectors o
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section, earlier in this chapter.Ex
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As explained in the “Combining ve
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Create a matrix with two columns.Cr
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Although the row names of the data
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you, because data frames are, in fa
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You can’t use logical vectors or
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askets.nlist baskets.nlist[‘scor
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The second line contains a $, which
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Part IIICoding in RIn this part . .
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Making the scriptSuppose you want t
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There’s no way you can define in
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Luckily, this problem doesn’t occ
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addPercent
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addPercent(new.numbers)Error in x *
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list instead of using the dots.So,
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code. So, instead of giving a funct
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Instead of passing the code of the
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Using internal functionsWriting you
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weird, think again about data frame
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print.default(small.one)$a[1] 1 2$b
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can easily add a default method exa
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carry out a certain task. Many prog
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if you have only one short line of
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you do so within a function and you
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second value of the result.4. A vec
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Luckily, R allows you to write all
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VAT client switch(client, private
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3. In each round through the loop,
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Page 235 and 236: If you get warning or error message
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Page 261 and 262: Chapter 12Getting Data into and out
Page 263 and 264: Using the Clipboard to copy and pas
Page 265 and 266: Using special characters in escape
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Page 309 and 310: with(cars, tapply(mpg, list(gear, a
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Page 319 and 320: Chapter 14Summarizing DataIn This C
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ange(cars$mpg)[1] 10.4 33.9Calculat
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As with most functions, you can sav
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Plotting histogramsTo get a clearer
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If this concept is unfamiliar to yo
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multiple variables, there’s a lot
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oxplot(mpg ~ cyl, data=cars)Figure
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Statisticians love it when they can
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You also can calculate the correlat
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with(cars, table(am, gear))3 4 5aut
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$ Var2: Factor w/ 2 levels “sick
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time specifying the margin argument
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Taking a Closer Look at Distributio
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Still, histograms leave much to the
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Now you want to do this for the tem
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Comparing Two SamplesComparing grou
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Again, you get the value for the te
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Many research questions revolve aro
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have to specify which margins you w
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str(InsectSprays)‘data.frame’:
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Checking the model tablesWith the m
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The difference between the means.Th
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The lm() function allows you to spe
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FunctionWhat It Doescoef()Returns a
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Model.anova Model.anovaAnalysis of
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predict(Model,newdata=new.cars, int
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Chapter 16Using Base GraphicsIn Thi
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The built-in R datasets are documen
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pch=21: Filled circlepch=22: Filled
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You also can use the function ablin
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It seems odd to use a plot function
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Figure 16-6: Adding main title, x-a
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Your graphic should look like Figur
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When your plot is complete, you nee
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getwd()[1] “C:/Users/Andrie”Nex
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Creating a Lattice PlotTo explore l
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Although cyl is a numeric vector, t
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into your R console.Changing Plot O
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xyplot(mpg ~ hp | factor(cyl), data
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Three-dimensional scatterplots: clo
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Notice that the function formula do
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millions of people. (The documentat
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Printing and Saving a Lattice PlotY
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Chapter 18Looking At ggplot2 Graphi
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aes() function to set up the mappin
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visual elements is the second eleme
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geom_point() Scatterplot stat_ident
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Creating line chartsTo create a lin
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Stat Description Default Geomstat_b
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Doing nothing with identitySometime
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Working with scalesIn ggplot2, scal
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Part VIThe Part of TensIn this part
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Then calculate the sum and mean for
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first supplied value as a fixed poi
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with(mtcars, length(mpg[hp > 150]))
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For example, to find the location o
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Your results should look similar to
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RGui and RStudio allow you to set t
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Reading the Package Manual and Vign
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Because the authors of R packages w
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AppendixInstalling R and RStudioBef
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a number of startup options by adap
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If you click Browse, you can select
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To access the cheat sheet specifica
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