R less than or equal to8/25/2023 One of the philosophies of R (and Unix more generally) is to have tools (or functions) that do specific things very well and then link these together, rather than a single multi-purpose tool that does many things poorly. If R has a built-in function for a particular task, it’s likely that function is highly optimized for that purpose and is your best option. It’s also important for your code to be readable, so that you and others can figure out what’s going on without too much hassle. Simple approaches that involve less typing are generally best. There are often several approaches to solving the same problem, particularly in R. Type seq_along(my_seq) to see it in action. However, as is the case with many common tasks, R has a separate built-in function for this purpose called seq_along(). One possibility is to combine the : operator and the length() function like this: 1:length(my_seq). In other words, we want a new vector (1, 2, 3, …) that is the same length as my_seq. Let’s pretend we don’t know the length of my_seq, but we want to generate a sequence of integers from 1 to N, where N represents the length of the my_seq vector. To do this, you need to include the object ‘my_seq’ as the value of argument ‘x’ of length(). To confirm that my_seq has length 30, we can use the length() function. You can actually use any abbreviation of the argument name, as long as it is different from any other argument. If you look closely again at the help file for ?seq, you will not see an argument “length =”, but only “length.out =”. Give it a shot now and store the result in a new variable called my_seq. Or maybe we don’t care what the increment is and we just want a sequence of 30 numbers between 5 and 10. OK, let’s say that instead of 1 to 20, we want a vector of numbers ranging from 0 to 10, incremented by 0.5. However, for complex functions it is often best practice to do so and makes your code much clearer.įor example, seq(from = 1, to = 20) will give the same output as seq(1, 20). In R, you do not have to specify the arguments by name if you write out their values in the same order as written in the function. The first two arguments are “from =” and “to =”. The help files show the arguments listed for the seq() function. The most basic use of seq() does exactly the same thing as the : operator. Often, we’ll desire more control over a sequence we’re creating than what the : operator gives us. If you don’t have a backtick key, you can use regular quotes.) (NOTE: The backtick (`) key is generally located in the top left corner of a keyboard, above the Tab key. However, in the case of an operator like the colon used above, you must enclose the symbol in backticks like this: ?. Remember that if you have questions about a particular R function, you can access its documentation with a question mark followed by the function name: ?function_name_here. It counted backwards in increments of 1! This is sometimes useful for plotting coefficients from models in reverse order. What happens if we do 15:1? Give it a try to find out. Note also that pi is one of the few constants built in to R. The upper limit of 10 is never reached, since the next number in our sequence would be greater than 10. The result is a vector of real numbers starting with pi (3.142…) and increasing in increments of 1. We could also use it to create a sequence of real numbers (a real number is a positive, negative, or 0 with an infinite or finite sequence of digits after the decimal place). That gave us every integer between (and including) 1 and 20 (an integer is a positive or negative counting number, including 0). The simplest way to create a sequence of numbers in R is by using the : operator. Sequences of numbers are used in many different tasks, from plotting the axes of graphs to generating simulated data. In this lesson, you’ll learn how to create sequences of numbers in R.
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