# Task 3: Cleaning the data¶

The data as loaded is not yet ready for our work. For technical reasons, the data representation has a few peculiarities:

- According to the data documentation, the value
`-9999`

indicates missing data. - Some data columns have been scaled by a factor.
- A wind direction of
`0`

means that it is*undetermined*,*North*is designated by`360`

.

## Tasks¶

- Replace the value
`-9999`

with something more appropriate, for example the constant`nan`

from the`math`

library. - Replace the measurements were no wind direction is given in a similar fashion.
- Now the value
`0`

is free to represent*North*as usual. This will come in handy in a later task. - Check for columns that have no useful data at all and remove them if convenient
- Re-scale the columns so they all use a factor of 1 (and can be read and interpreted more easily by humans)
- Check if there are entries missing for some dates/hours.
Consider first how many hours the given year should have (Account for the additional day of leap years if applicable.)
How many rows are missing in your data set? (If your data set has a significant number of rows missing, consider choosing another one.)
For this you may find the
`pandas.date_range()`

-function useful. - Add suitable placeholders for those missing rows, so the averaging works as expected.

## Hints for Solving the Task

If you are seriously stuck, you can take a look at the solution hints.