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## to Space Age in the R Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

Given an age in seconds, calculate how old someone would be on:

• Earth: orbital period 365.25 Earth days, or 31557600 seconds
• Mercury: orbital period 0.2408467 Earth years
• Venus: orbital period 0.61519726 Earth years
• Mars: orbital period 1.8808158 Earth years
• Jupiter: orbital period 11.862615 Earth years
• Saturn: orbital period 29.447498 Earth years
• Uranus: orbital period 84.016846 Earth years
• Neptune: orbital period 164.79132 Earth years

So if you were told someone were 1,000,000,000 seconds old, you should be able to say that they're 31.69 Earth-years old.

If you're wondering why Pluto didn't make the cut, go watch this youtube video.

## Installation

See this guide for instructions on how to setup your local R environment.

## How to implement your solution

In each problem folder, there is a file named `<exercise_name>.R` containing a function that returns a `NULL` value. Place your implementation inside the body of the function.

## How to run tests

Inside of RStudio, simply execute the `test_<exercise_name>.R` script. This can be conveniently done with testthat's `auto_test` function. Because exercism code and tests are in the same folder, use this same path for both `code_path` and `test_path` parameters. On the command-line, you can also run `Rscript test_<exercise_name>.R`.

## Source

Partially inspired by Chapter 1 in Chris Pine's online Learn to Program tutorial. http://pine.fm/LearnToProgram/?Chapter=01

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### test_space-age.R

``````source("./space-age.R")
library(testthat)

context("space age")

test_that("Age on Earth", {
seconds <- 1000000000
expect_equal(space_age(seconds, "earth"), 31.69)
})

test_that("Age on Mercury", {
seconds <- 2134835688
expect_equal(space_age(seconds, "mercury"), 280.88)
})

test_that("Age on Venus", {
seconds <- 189839836
expect_equal(space_age(seconds, "venus"), 9.78)
})

test_that("Age on Mars", {
seconds <- 2329871239
expect_equal(space_age(seconds, "mars"), 39.25)
})

test_that("Age on Jupiter", {
seconds <- 901876382
expect_equal(space_age(seconds, "jupiter"), 2.41)
})

test_that("Age on Saturn", {
seconds <- 3000000000
expect_equal(space_age(seconds, "saturn"), 3.23)
})

test_that("Age on Uranus", {
seconds <- 3210123456
expect_equal(space_age(seconds, "uranus"), 1.21)
})

test_that("Age on Neptune", {
seconds <- 8210123456
expect_equal(space_age(seconds, "neptune"), 1.58)
})

message("All tests passed for exercise: space-age")``````
``````space_age <- function(seconds, planet) {

# switch provided planet name with its relative orbital period
convert <- function(planet) {
switch(planet,
"mercury" = 0.2408467,
"venus"   = 0.61519726,
"earth"   = 1,
"mars"    = 1.8808158,
"jupiter" = 11.862615,
"saturn"  = 29.447498,
"uranus"  = 84.016846,
"neptune" = 164.79132)
}

# divide given age by product of sec_per_Earth_year and relative orbital period
round(seconds / (31557600 * convert(planet)), 2)
}``````

## Community comments

Find this solution interesting? Ask the author a question to learn more.

### What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

• What compromises have been made?
• Are there new concepts here that you could read more about to improve your understanding?