SS: Type “1+3” into your new script window
1 + 3 #AC: Addition
## [1] 4
SS:'rain' contains actual rainfall data for Boulder, CO (2000-2011)
rain <- c(16, 18, 14, 22, 27, 17, 19, 17, 17, 22, 20, 22)
AC: c() is the combine function; it can create an object from a list of data.
SS: Try using the functions sum() and length() to clacluate the mean amount of rainfall, check your answer using the mean function.
sum(rain)/length(rain)
## [1] 19.25
sum(rain)/length(rain) == mean(rain)
## [1] TRUE
AC: It returns TRUE, so I have correctly calculated the mean.
rain - 1 #AC: Subtraction
## [1] 15 17 13 21 26 16 18 16 16 21 19 21
rain^2 #AC: Powers
## [1] 256 324 196 484 729 289 361 289 289 484 400 484
sqrt(rain) #AC: Square Root Function
## [1] 4.000 4.243 3.742 4.690 5.196 4.123 4.359 4.123 4.123 4.690 4.472
## [12] 4.690
SS: Using the four steps above compute the standard deviation of the rainfall data.
SS: You have the correct answer if you get something close to 3.4.
rain.dev <- rain - mean(rain) #AC: Step 1: take deviations from mean
rain.dev.sq <- rain.dev^2 #AC:Step 2: square the deviations
rain.dev.sq.mean <- mean(rain.dev.sq) #AC: Step 3: Take the mean of square deviations
rain.std.dev <- sqrt(rain.dev.sq.mean) #AC: Step 4: Take the square root of the mean square deviations (hence RMS = root mean square).
rain.std.dev
## [1] 3.394
AC: It returns 3.394235
SS: Now, complete the return statement below to create a function to convert inches to centimeters.
in_to_cm <- function(someDataInInches) {
return(someDataInInches/0.3937) #complete the return statement
} #SS: someDataInInches is just a placeholder; AC: Use a name that will make sense for the placeholder
in_to_cm(1)
## [1] 2.54
AC: To test, I know that 1 should return 2.54 because 1in = 2.54cm. It checks out.
SS: Write a function to compute the standard deviation, use the four steps outlined above.
stdevp <- function(someData) {
return(sqrt(mean((someData - mean(someData))^2)))
}
stdevp(rain) #AC: Returns 3.394235; it checks out.
## [1] 3.394
stdevp(rain) == rain.std.dev #AC: And this statement returns TRUE.
## [1] TRUE