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sibyvt/Assignment: swirl Lesson 1: Basic Building Blocks

Created May 12, 2016 17:46
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Assignment: swirl Lesson 1: Basic Building Blocks
| In this lesson, we will explore some basic building blocks of the R
| programming language.
...
|
|== | 3%
| If at any point you'd like more information on a particular topic related to
| R, you can type help.start() at the prompt, which will open a menu of
| resources (either within RStudio or your default web browser, depending on
| your setup). Alternatively, a simple web search often yields the answer
| you're looking for.
...
|
|==== | 5%
| In its simplest form, R can be used as an interactive calculator. Type 5 + 7
| and press Enter.
>
> 5+5
[1] 10
| One more time. You can do it! Or, type info() for more options.
| Type 5 + 7 and press Enter.
> 5+7
[1] 12
| You nailed it! Good job!
|
|====== | 8%
| R simply prints the result of 12 by default. However, R is a programming
| language and often the reason we use a programming language as opposed to a
| calculator is to automate some process or avoid unnecessary repetition.
...
|
|======= | 11%
| In this case, we may want to use our result from above in a second
| calculation. Instead of retyping 5 + 7 every time we need it, we can just
| create a new variable that stores the result.
...
|
|========= | 13%
| The way you assign a value to a variable in R is by using the assignment
| operator, which is just a 'less than' symbol followed by a 'minus' sign. It
| looks like this: <-
...
|
|=========== | 16%
| Think of the assignment operator as an arrow. You are assigning the value on
| the right side of the arrow to the variable name on the left side of the
| arrow.
...
|
|============= | 18%
| To assign the result of 5 + 7 to a new variable called x, you type x <- 5 +
| 7. This can be read as 'x gets 5 plus 7'. Give it a try now.
> x<-5+7
| Excellent job!
|
|=============== | 21%
| You'll notice that R did not print the result of 12 this time. When you use
| the assignment operator, R assumes that you don't want to see the result
| immediately, but rather that you intend to use the result for something else
| later on.
...
|
|================= | 24%
| To view the contents of the variable x, just type x and press Enter. Try it
| now.
> x
[1] 12
| You are amazing!
|
|================== | 26%
| Now, store the result of x - 3 in a new variable called y.
> y<-x-3
| You are quite good my friend!
|
|==================== | 29%
| What is the value of y? Type y to find out.
> y
[1] 9
| Nice work!
|
|====================== | 32%
| Now, let's create a small collection of numbers called a vector. Any object
| that contains data is called a data structure and numeric vectors are the
| simplest type of data structure in R. In fact, even a single number is
| considered a vector of length one.
...
|
|======================== | 34%
| The easiest way to create a vector is with the c() function, which stands for
| 'concatenate' or 'combine'. To create a vector containing the numbers 1.1, 9,
| and 3.14, type c(1.1, 9, 3.14). Try it now and store the result in a variable
| called z.
> cc(1.1, 9, 3.14)
Error: could not find function "cc"
> c(1.1, 9, 3.14)
[1] 1.10 9.00 3.14
| Give it another try. Or, type info() for more options.
| Inputting z <- c(1.1, 9, 3.14) will assign the vector (1.1, 9, 3.14) to a new
| variable called z. Including single spaces after the commas in the vector is
| not required, but helps make your code less cluttered and more readable.
> z<-c(1.1, 9, 3.14)
| Excellent work!
|
|========================== | 37%
| Anytime you have questions about a particular function, you can access R's
| built-in help files via the `?` command. For example, if you want more
| information on the c() function, type ?c without the parentheses that
| normally follow a function name. Give it a try.
> ?c
| Keep working like that and you'll get there!
|
|============================ | 39%
| Type z to view its contents. Notice that there are no commas separating the
| values in the output.
> z
[1] 1.10 9.00 3.14
| You are really on a roll!
|
|============================= | 42%
| You can combine vectors to make a new vector. Create a new vector that
| contains z, 555, then z again in that order. Don't assign this vector to a
| new variable, so that we can just see the result immediately.
> c(z,555,z)
[1] 1.10 9.00 3.14 555.00 1.10 9.00 3.14
| All that practice is paying off!
|
|=============================== | 45%
| Numeric vectors can be used in arithmetic expressions. Type the following to
| see what happens: z * 2 + 100.
> z*2+10
[1] 12.20 28.00 16.28
| Try again. Getting it right on the first try is boring anyway! Or, type
| info() for more options.
| Enter z * 2 + 100, without assigning the result to a variable. The `*` symbol
| is used for multiplication and shares a key with the number 8 on many
| keyboards.
> z*2+100
[1] 102.20 118.00 106.28
| That's correct!
|
|================================= | 47%
| First, R multiplied each of the three elements in z by 2. Then it added 100
| to each element to get the result you see above.
...
|
|=================================== | 50%
| Other common arithmetic operators are `+`, `-`, `/`, and `^` (where x^2 means
| 'x squared'). To take the square root, use the sqrt() function and to take
| the absolute value, use the abs() function.
...
|
|===================================== | 53%
| Take the square root of z - 1 and assign it to a new variable called my_sqrt.
> sqrt(z-1)
[1] 0.3162278 2.8284271 1.4628739
| Keep trying! Or, type info() for more options.
| Assign the result of sqrt(z - 1) to a variable called my_sqrt.
> my_sqrt<-sqrt(z-)
Error: unexpected ')' in "my_sqrt<-sqrt(z-)"
> my_sqrt<-sqrt(z-1)
| You nailed it! Good job!
|
|======================================= | 55%
| Before we view the contents of the my_sqrt variable, what do you think it
| contains?
1: a vector of length 3
2: a vector of length 0 (i.e. an empty vector)
3: a single number (i.e a vector of length 1)
Selection: 1
| You nailed it! Good job!
|
|========================================= | 58%
| Print the contents of my_sqrt.
> my_sqrt()
Error: could not find function "my_sqrt"
> print(my_sqrt)
[1] 0.3162278 2.8284271 1.4628739
| Give it another try. Or, type info() for more options.
| Just type my_sqrt and press Enter to view its value.
> my_sqrt
[1] 0.3162278 2.8284271 1.4628739
| You got it!
|
|========================================== | 61%
| As you may have guessed, R first subtracted 1 from each element of z, then
| took the square root of each element. This leaves you with a vector of the
| same length as the original vector z.
...
|
|============================================ | 63%
| Now, create a new variable called my_div that gets the value of z divided by
| my_sqrt.
> my_div<-(z/my_sqrt)
| Nice try, but that's not exactly what I was hoping for. Try again. Or, type
| info() for more options.
| Enter my_div <- z / my_sqrt. The spaces on either side of the `/` sign are
| not required, but can often improve readability by making code appear less
| cluttered. In the end, it's personal preference.
> my_div<-z/my_sqrt
| Keep up the great work!
|
|============================================== | 66%
| Which statement do you think is true?
1: my_div is undefined
2: The first element of my_div is equal to the first element of z divided by the first element of my_sqrt, and so on...
3: my_div is a single number (i.e a vector of length 1)
Selection: 2
| You nailed it! Good job!
|
|================================================ | 68%
| Go ahead and print the contents of my_div.
> my_div
[1] 3.478505 3.181981 2.146460
| Perseverance, that's the answer.
|
|================================================== | 71%
| When given two vectors of the same length, R simply performs the specified
| arithmetic operation (`+`, `-`, `*`, etc.) element-by-element. If the vectors
| are of different lengths, R 'recycles' the shorter vector until it is the
| same length as the longer vector.
...
|
|==================================================== | 74%
| When we did z * 2 + 100 in our earlier example, z was a vector of length 3,
| but technically 2 and 100 are each vectors of length 1.
...
|
|===================================================== | 76%
| Behind the scenes, R is 'recycling' the 2 to make a vector of 2s and the 100
| to make a vector of 100s. In other words, when you ask R to compute z * 2 +
| 100, what it really computes is this: z * c(2, 2, 2) + c(100, 100, 100).
...
|
|======================================================= | 79%
| To see another example of how this vector 'recycling' works, try adding c(1,
| 2, 3, 4) and c(0, 10). Don't worry about saving the result in a new variable.
> c(1,2,3,4)+c(0,10)
[1] 1 12 3 14
| All that hard work is paying off!
|
|========================================================= | 82%
| If the length of the shorter vector does not divide evenly into the length of
| the longer vector, R will still apply the 'recycling' method, but will throw
| a warning to let you know something fishy might be going on.
...
|
|=========================================================== | 84%
| Try c(1, 2, 3, 4) + c(0, 10, 100) for an example.
> c(1, 2, 3, 4) + c(0, 10, 100)
[1] 1 12 103 4
Warning message:
In c(1, 2, 3, 4) + c(0, 10, 100) :
longer object length is not a multiple of shorter object length
| Your dedication is inspiring!
|
|============================================================= | 87%
| Before concluding this lesson, I'd like to show you a couple of time-saving
| tricks.
...
|
|=============================================================== | 89%
| Earlier in the lesson, you computed z * 2 + 100. Let's pretend that you made
| a mistake and that you meant to add 1000 instead of 100. You could either
| re-type the expression, or...
...
|
|================================================================ | 92%
| In many programming environments, the up arrow will cycle through previous
| commands. Try hitting the up arrow on your keyboard until you get to this
| command (z * 2 + 100), then change 100 to 1000 and hit Enter. If the up arrow
| doesn't work for you, just type the corrected command.
>
> c(1, 2, 3, 4) + c(0, 10, 1000)
[1] 1 12 1003 4
Warning message:
In c(1, 2, 3, 4) + c(0, 10, 1000) :
longer object length is not a multiple of shorter object length
| Nice try, but that's not exactly what I was hoping for. Try again. Or, type
| info() for more options.
| If your environment does not support the up arrow feature, then just type the
| corrected command to move on.
> z*2+1000
[1] 1002.20 1018.00 1006.28
| Perseverance, that's the answer.
|
|================================================================== | 95%
| Finally, let's pretend you'd like to view the contents of a variable that you
| created earlier, but you can't seem to remember if you named it my_div or
| myDiv. You could try both and see what works, or...
...
|
|==================================================================== | 97%
| You can type the first two letters of the variable name, then hit the Tab key
| (possibly more than once). Most programming environments will provide a list
| of variables that you've created that begin with 'my'. This is called
| auto-completion and can be quite handy when you have many variables in your
| workspace. Give it a try. (If auto-completion doesn't work for you, just type
| my_div and press Enter.)
> my_div
[1] 3.478505 3.181981 2.146460
| Keep working like that and you'll get there!
|
|======================================================================| 100%
| Would you like to receive credit for completing this course on Coursera.org?
1: No
2: Yes
Selection: 2
What is your email address? [email protected]
What is your assignment token? Mj94HXH2Ty2k1bjM
Grade submission succeeded!
@mswest1
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mswest1 commented Jul 10, 2021

Very helpful for me learning R basics!!! :)

@Robert2Connolly
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Thanks for the tip, I will definitely use it. Right now I'm working on a project for service https://essays.edubirdie.com/research-proposal-writing-service with research proposal writing for students. That way we are trying to help with training so that students can learn more quickly and have the opportunity to start working on their careers while they are still at university.

@Parimahajializadeh
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Very helpful, thank you

@Aus-tin
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Aus-tin commented Mar 27, 2023

very helpful, thank you so much

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