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You could drop the argument pph and just multiply hours by 40. But thatwould mean that if, for example, your colleague uses a different hourly rate,he would have to change the value in the body of the function in order to beable to use it. It’s good coding practice to use arguments with default valuesfor any value that can change. Doing so makes a function more flexible andusable.Now imagine you have some big clients that give you a lot of work. To keepthem happy, you decide to give them a reduction of 10 percent on the price perhour for orders that involve more than 100 hours of work. So, if the number ofhours worked is larger than 100, you calculate the new price by multiplying theprice by 0.9. You can write that almost literally in your code like this:priceCalculator priceCalculator(hours = 110)[1] 3960An if statement in R consists of three elements: the keyword if, a singlelogical value between parentheses, and a block of code between braces thathas to be executed when the logical value is TRUE. If you look at the ifstatement in the previous function, you find these three elements. Betweenthe parentheses, you find an expression (hours > 100) that evaluates to asingle logical value. Between the braces stands one line of code that reducesthe net price by 10 percent when the line is carried out.This construct is the most general way you can specify an if statement. But
if you have only one short line of code in the code block, you don’t have to putbraces around it. You can change the complete if statement in the functionwith the following line:if(hours > 100) net.price
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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
Page 159 and 160: Using the creator functionsYou can
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Page 163 and 164: [1] 6Likewise, the ncol() function
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Page 169 and 170: As explained in the “Combining ve
Page 171 and 172: Create a matrix with two columns.Cr
Page 173 and 174: Although the row names of the data
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Page 179 and 180: askets.nlist baskets.nlist[‘scor
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Page 183 and 184: Part IIICoding in RIn this part . .
Page 185 and 186: Making the scriptSuppose you want t
Page 187 and 188: There’s no way you can define in
Page 189 and 190: Luckily, this problem doesn’t occ
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Page 193 and 194: addPercent(new.numbers)Error in x *
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Page 197 and 198: code. So, instead of giving a funct
Page 199 and 200: Instead of passing the code of the
Page 201 and 202: Using internal functionsWriting you
Page 203 and 204: weird, think again about data frame
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Page 207 and 208: can easily add a default method exa
Page 209: carry out a certain task. Many prog
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Page 215 and 216: second value of the result.4. A vec
Page 217 and 218: Luckily, R allows you to write all
Page 219 and 220: VAT client switch(client, private
Page 221 and 222: 3. In each round through the loop,
Page 223 and 224: workspace. This may be exactly what
Page 225 and 226: Applying functions on rows and colu
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Page 231 and 232: Chapter 10Debugging Your CodeIn Thi
Page 233 and 234: R always tells you in which code th
Page 235 and 236: If you get warning or error message
Page 237 and 238: logit() function. Even more, the tr
Page 239 and 240: When you’re in browser mode, you
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Page 243 and 244: In logit(as.numeric(x)/100) : x not
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Page 247 and 248: If you want to know the median numb
Page 249 and 250: typing help(paste) returns help abo
Page 251 and 252: From the description of ada::update
Page 253 and 254: Getting Involved in the R Community
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Chapter 12Getting Data into and out
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Using the Clipboard to copy and pas
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Using special characters in escape
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‘data.frame’: 10 obs. of 9 vari
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XLConnect also can write Excel file
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These functions need a specific fil
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Working with Files and FoldersYou k
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[1] “F:/git/roxygen2/roxygen2/REA
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can confirm this by taking a close
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But in many practical situations, y
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$: The dollar-sign operator selects
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To illustrate subsetting of data fr
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customary to specify a so-called se
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Specify a logical vector, where FAL
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After a short while of writing subs
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following:> frost head(frost, 5)Al
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Figure 13-1: Different ways of comb
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function tries to identify columns
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Both data frames have a variable Na
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time, %in% is in infix operator. An
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order. Do this using the order() fu
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Sorting multiple columns in mixed o
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FUN: The function to apply (for exa
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5.843333 3.057333 3.758000 1.199333
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with(cars, tapply(mpg, list(gear, a
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+ y ~ a + b Include columns a as we
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In the world of R, people usually r
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Now you can start. First, create so
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data: A molten data frame.formula:
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Chapter 14Summarizing DataIn This C
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that benefits from being converted
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With this dataset in your workspace
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ange(cars$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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