[R] about data manipulation

[Jim Lemon]

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.
>
>         [[alternative HTML version deleted]]
>
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