[R] Count objects and print it into a new variable

[saba]

Hello,

I used R a year ago. With the data I am working with now, I realized that I
need to go back to R. Unfortunately, my memory is not my friend if it comes
down to coding :-)

What I want to do is extract the length of a variable of a file with certain
conditions and then print this number in a new variable..

My file (yukon), contains information about fires in the Yukon Territory,
and it looks basically like this:

Fire_Year Area_Hecta InitialFir ... and other headers but they are not
important

The Fire_Year ranges from 1980-2010, the Area_Hecta contains numbers and the
InitialFir contains a date written like this: 24/05/1980 

My end goal is to plot 2 plots, one with the summed area burned per year and
the other plot should show the number of fires happening per year.

I managed the first plot with the command aggregate.

annualAB.sum<-aggregate(yukon$Area_Hecta~yukon$Fire_Year, sum, data=yukon)

Now I am having troubles with the second plot. I created subsets for each
year and then used the length command..then I could take all those numbers
and put them in a new variable...

y1980 <- subset(yukon,Fire_Year=="1980")
length(y1980$Area_Hecta)

but I somehow feel that there must be a better solution...maybe a loop?

Any help is greatly appreciated
Thanks so much
Sandra



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