[R] Sum by column

[Peter Francis]

Dear List,

I have a question of convenience,

I am looking to sum the values of one column based on another column - a example may help explain better!

ED			ECOCODE
21.809467	AA0101
36.229566	PA1201
51.861284	PA1201
11.36232	PA1201
27.264634	PA1201
12.261986	PA1201
46.519313	PA1201
7.815376	PA1201
2.810428	PA1201
13.478372	PA1201
35.670182	PA1301
27.128715	AT0801
19.010294	AT1201
15.475368	AT1201
18.597983	AT0101
29.292615	AT0101
6.749846	AT0101
14.981488	AT0101
14.93511	AT0101
14.93511	AT0101
21.040785	AT0101
8.271615	AT0101
12.94232	AT0101
6.749846	AT0101
15.484412	AT0101
29.644494	AT0101
43.211212	AT0101

So for AA0101 it would be = 21.809467
	    AT1201 it would be = 19.010294+15.475368

etc

I would then like to be able to output a table with ECOCODE in one column and the sum of ED in the other.

This is stored in a dataframe called ecoregion, i understand people like having code to change but i have none as i am a relative beginner! Sorry in advance!

Thanks 

Peter