Hi lily, If you want to use aggregate, supply the name of the function: aggregate(flow~year, data=df, "sum") You can also use "by" like this by(df$flow,df$year,FUN=sum) I assume that you don't have to worry about missing months in a year. Jim :
On Thu, Dec 1, 2016 at 3:06 PM, lily li <chocold12 at gmail.com> wrote:
Hi R users,
I'm trying to manipulate dataset, but met some difficulties.
df
year month flow
2006 3 3.5
2006 4 3.8
2006 5 21
2006 6 32
2007 3 4.1
2007 4 4.4
...
I want to calculate total flow for each year, and use the code below:
aggregate(flow~year, data=df, sum)
But it gave the error message:
Error in get(as.character(FUN), mode = "function", envir = envir) :
object 'FUN' of mode 'function' was not found
What is the problem and how to solve it? Thanks for your help.
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