Merge and aggregate datasets


;Task:
Merge and aggregate two datasets as provided in   '''.csv'''   files into a new resulting dataset.

Use the appropriate methods and data structures depending on the programming language. 

Use the most common libraries only when built-in functionality is not sufficient.


;Note:
Either load the data from the   '''.csv'''   files or create the required data structures hard-coded.


'''patients.csv'''   file contents:
<pre>
PATIENT_ID,LASTNAME
1001,Hopper
4004,Wirth
3003,Kemeny
2002,Gosling
5005,Kurtz
</pre>


'''visits.csv''' &nbsp; file contents:
<pre>
PATIENT_ID,VISIT_DATE,SCORE
2002,2020-09-10,6.8
1001,2020-09-17,5.5
4004,2020-09-24,8.4
2002,2020-10-08,
1001,,6.6
3003,2020-11-12,
4004,2020-11-05,7.0
1001,2020-11-19,5.3
</pre>


Create a resulting dataset in-memory or output it to screen or file, whichever is appropriate for the programming language at hand.

Merge and group per patient id and last name, &nbsp; get the maximum visit date, &nbsp; and get the sum and average of the scores per patient to get the resulting dataset.


Note that the visit date is purposefully provided as ISO format, &nbsp; so that it could also be processed as text and sorted alphabetically to determine the maximum date.
<pre>
| PATIENT_ID | LASTNAME | LAST_VISIT |  SCORE_SUM | SCORE_AVG |
| 1001       |  Hopper  | 2020-11-19 |  17.4      | 5.80      |
| 2002       |  Gosling | 2020-10-08 |   6.8      | 6.80      |
| 3003       |  Kemeny  | 2020-11-12 |            |           |
| 4004       |  Wirth   | 2020-11-05 |  15.4      | 7.70      |
| 5005       |  Kurtz   |            |            |           |
</pre>


;Note:
This task is aimed in particular at programming languages that are used in data science and data processing, such as F#, Python, R, SPSS, MATLAB etc.


;Related tasks:
* [[CSV data manipulation]]
* [[CSV to HTML translation]]
* [[Read entire file]]
* [[Read a file line by line]]
<br><br>