**R-exercises**, and kindly contributed to R-bloggers)

While understanding and spending time improving specific techniques, and strengthening indvidual muscles is important, occasionally it is necessary to do some rounds of actual sparring to see your flow and spot weaknesses. This exercise sets forces you to use all that you have practiced: to scrape links, download data, regular expressions, merge data and then analyze it.

We will download data from the website football-data.co.uk that has data on some football/soccer leagues results and odds quoted by bookmakers where you can bet on the results.

Answers are available here.

**Exercise 1**

Use R to scan the German section on football-data.co.uk for any links and save them in a character vector called `all_links`

. There are many ways to accomplish this.

**Exercise 2**

Among the links you found should be a number pointing to comma-separated values files with data on Bundesliga 1 and 2 separated by season. Now update `all_links`

vector so that only links to `csv`

files remain. Use regular expressions.

**Exercise 3**

Again, update `all_links`

so that only links to csv tables ‘from Bundesliga 1 from Season 1993/1994 to 2013/2014 inclusive’ remain.

**Exercise 4**

Import to a list in your workspace all the 21 remaining csv files in `all_links`

, each one as a `data.frame`

. Use `read.csv`

, with the url and `na.strings = c("", "NA")`

. Not that you might need to add a prefix for them, so the links are complete.

**Exercise 5**

Take the list and generate a one big data.frame with all the `data.frame`

s previously imported. One way to do this is using `rbind.fill`

function from a well-known package. Name the new `data.frame`

as `bundesl`

.

**Exercise 6**

Take a good look at the new dataset. Our `read.csv`

did not work perfectly on this data: it turns out that there are some empty rows and empty columns, identify and count them. Update the `bundesl`

so it no longer has empty rows m nor columns.

**Exercise 7**

Format the Date column so R understands using `as.Date()`

.

**Exercise 8**

Remove all columns which are not 100% complete, and the variable `Div`

as well.

**Exercise 9**

Which are the top 3 teams in terms of numbers of wins in Bundesliga 1 for our period? You are free to use base-R functions or any package. Be warned that his task is not as simple as it seems due the nature in the data and small inconsitency in the data.

**Exercise 10**

Which team has held the longest winning streak in our data?

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**R-exercises**.

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