### 3. Creating sequences We just learned about the `c()` operator, which forms a vector from its arguments. If we're trying to build a vector containing a sequence of numbers, there are several useful functions at our disposal. These are the colon operator `:` and the sequence function `seq()`. ##### `:` Colon operator: ```{r} 1:10 # Numbers 1 to 10 127:132 # Numbers 127 to 132 ``` ##### `seq` function: `seq(from, to, by)` ```{r} seq(1,10,1) # Numbers 1 to 10 seq(1,10,2) # Odd numbers from 1 to 10 seq(2,10,2) # Even numbers from 2 to 10 ``` > To learn more about a function, type `?functionname` into your console. E.g., `?seq` pulls up a Help file with the R documentation for the `seq` function. #### (a) Use `:` to output the sequence of numbers from 3 to 12 ```{r} 3:12 ``` #### (b) Use `seq()` to output the sequence of numbers from 3 to 30 in increments of 3 ```{r} seq(3, 30, 3) ``` #### (c) Save the sequence from (a) as a variable `x`, and the sequence from (b) as a variable `y`. Output their product `x*y` ```{r} x <- 3:12 y <- seq(3, 30, 3) x * y ```

### 4. Cars data We'll look at data frame and plotting in much more detail in later classes. For a previous of what's to come, here's a very basic example. For this example we'll use a very simple dataset. The `cars` data comes with the default installation of R. To see the first few columns of the data, just type `head(cars)`. ```{r} head(cars) ``` We'll do a bad thing here and use the `attach()` command, which will allow us to access the `speed` and `dist` columns of `cars` as though they were vectors in our workspace. ```{r} attach(cars) # Using this command is poor style. We will avoid it in the future. speed dist ``` #### (a) Calculate the average and standard deviation of speed and distance. ```{r} mean(speed) sd(speed) mean(dist) sd(dist) ```

We can easily produce a histogram of stopping distance using the `hist` function. ```{r} hist(dist) # Histogram of stopping distance ``` The `plot(x,y,...)` function plots a vector `y` against a vector `x`. You can type `?plot` into the Console to learn more about the basic plot function. #### (b) Use the `plot(x,y)` function to create a scatterplot of dist against speed. ```{r} plot(speed, dist) ```