![]() So, it is a good idea to not use names that are already taken: my_number <- 1 R is case-sensitive, so name and Name will refer to different objects:įinally, R will overwrite any previous information stored in an object without asking you for permission. Wherever R encounters the object, it will replace it with the data saved inside, like so: a <- 1 For example, you can save data into an object like a or b. What is an object? Just a name that you can use to call up stored data. R lets you save data by storing it inside an R object. If you want to use those numbers again, you’ll have to ask your computer to save them somewhere. What you are looking at is basically the footprints of six numbers that existed briefly and then melted back into your computer’s RAM. Running 1:6 generated a vector of numbers for you to see, but it didn’t save that vector anywhere in your computer’s memory. That’s all there is to how a virtual die looks! But you are not done yet. The : operator returns its results as a vector, a one-dimensional set of numbers: 1 : 6 The : operator from a couple of pages ago gives you a nice way to create a group of numbers from one to six. Now that you know how to use R, let’s use it to make a virtual die. I’ll avoid showing >s and s unless I want you to look at them. I’ll use a single hashtag to add my own comments and a double hashtag, #, to display the results of code. The hashtag is known as the commenting symbol in R.įor the remainder of the book, I’ll use hashtags to display the output of R code. Humans will be able to read the comments, but your computer will pass over them. This makes hashtags very useful for adding comments and annotations to your code. R treats the hashtag character, #, in a special way R will not run anything that follows a hashtag on a line. This will make the code easier to copy and paste if you want to put it in your own console. For example, you could do some basic arithmetic: 2 * 3ĭid you notice something different about this code? I’ve left out the >’s and ’s. Once you get the hang of the command line, you can easily do anything in R that you would do with a calculator. You can then try a different command at the next prompt: > 3 % 5 R is just telling you that your computer couldn’t understand or do what you asked it to do. If you ever see an error message, don’t panic. If you type a command that R doesn’t recognize, R will return an error message. Either finish the command or hit Escape to start over: > 5. If you type an incomplete command and press Enter, R will display a + prompt, which means R is waiting for you to type the rest of your command. R is a dynamic programming language, which means R automatically interprets your code as you run it. If you’ve programmed in such a language before, you may wonder whether you have to compile your R code before you can use it. In some languages, like C, Java, and FORTRAN, you have to compile your human-readable code into machine-readable code (often 1s and 0s) before you can run it. You can mostly ignore the numbers that appear in brackets: > 100:130 These numbers just mean that the second line begins with the 14th value in the result, and the third line begins with the 25th value. Notice that new bracketed numbers appear at the start of the second and third lines of output. For example, the command 100:130 returns 31 values it creates a sequence of integers from 100 to 130. Some commands return more than one value, and their results may fill up multiple lines. ![]() R is just letting you know that this line begins with the first value in your result. You’ll notice that a appears next to your result. For example, if you type 1 + 1 and hit Enter, RStudio will display: > 1 + 1 ![]() Then RStudio displays a fresh prompt for your next command. When you type a command at the prompt and hit Enter, your computer executes the command and shows you the results. The line you type it into is called the command line. The code you type is called a command, because it will command your computer to do something for you. You type R code into the bottom line of the RStudio console pane and then click Enter to run it. The appendix will give you an overview of the two free tools and tell you how to download them. If you do not yet have R and RStudio intalled on your computer–or do not know what I am talking about–visit Appendix A.
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