Basically what its on the title, I have a csv that I converted into a pandas dataframe that its something like this:

```
"ID","Name","Sex","Age","Height","Weight","Team","NOC","Games","Year","Season","City","Sport","Event","Medal"
"1","A Dijiang","M",24,180,80,"China","CHN","1992 Summer",1992,"Summer","Barcelona","Basketball","Basketball Men's Basketball",NA
"2","A Lamusi","M",23,170,60,"China","CHN","2012 Summer",2012,"Summer","London","Judo","Judo Men's Extra-Lightweight",NA
"3","Gunnar Nielsen Aaby","M",24,NA,NA,"Denmark","DEN","1920 Summer",1920,"Summer","Antwerpen","Football","Football Men's Football",NA
"4","Edgar Lindenau Aabye","M",34,NA,NA,"Denmark/Sweden","DEN","1900 Summer",1900,"Summer","Paris","Tug-Of-War","Tug-Of-War Men's Tug-Of-War","Gold"
"5","Christine Jacoba Aaftink","F",21,185,82,"Netherlands","NED","1988 Winter",1988,"Winter","Calgary","Speed Skating","Speed Skating Women's 500 metres",NA

```

I would like to obtain the mean of 'Height' based on the Years like having the mean of the year 1992 and so on