Does this do what you want?

> x <- "Species BA
+ ACSA    55.7632696
+ FRAM    122.9933524
+ ACSA    67.54424205
+ ACSA    89.22123136
+ ACSA    82.46680716
+ ACSA    22.46238747
+ ACSA    19.94911335
+ ACSA    20.42035225
+ ACSA    19.00663555
+ ACSA    21.67698931
+ ACSA    57.80530483
+ ACSA    30.31636911
+ Dead    43.98229715
+ Dead    40.21238597
+ Dead    16.49336143
+ Dead    40.21238597
+ Dead    16.49336143
+ ACSA    78.53981634
+ VIPR    3.926990817
+ AEGL    11.78097245
+ AEGL    0
+ AEGL    0
+ ACSA    0
+ ACSA    0
+ ACSA    0
+ VIPR    0"
> x <- read.table(textConnection(x), header=TRUE)
> # compute area for each species
> y <- tapply(x$BA, x$Species, sum)
> # get ratio
> y/sum(x$BA)
       ACSA        AEGL        Dead        FRAM        VIPR
0.656210104 0.013678643 0.182746672 0.142805034 0.004559548
>
>



On 7/1/07, James R. Milks <james.milks@wright.edu> wrote:
>
> I have a data frame with two columns, one of which is a factor
> (Species) and the other is numeric (BA, which stands for basal
> area).  Here's a sample:
>
>
> Species BA
> ACSA    55.7632696
> FRAM    122.9933524
> ACSA    67.54424205
> ACSA    89.22123136
> ACSA    82.46680716
> ACSA    22.46238747
> ACSA    19.94911335
> ACSA    20.42035225
> ACSA    19.00663555
> ACSA    21.67698931
> ACSA    57.80530483
> ACSA    30.31636911
> Dead    43.98229715
> Dead    40.21238597
> Dead    16.49336143
> Dead    40.21238597
> Dead    16.49336143
> ACSA    78.53981634
> VIPR    3.926990817
> AEGL    11.78097245
> AEGL    0
> AEGL    0
> ACSA    0
> ACSA    0
> ACSA    0
> VIPR    0
>
> I would like to calculate relative basal area for each species in
> this plot.  For that, I need to divide the total basal area per
> species by the total basal area in the plot.  Getting the total basal
> area in the plot is easy.  However, I'm mystified on how to get the
> total basal area per species.  Is there a way to extract and/or sum
> the total basal area per species?
>
> Thank you in advance.
>
> Jim Milks
>
> Graduate Student
> Environmental Sciences Ph.D. Program
> Wright State University
> 3640 Colonel Glenn Hwy
> Dayton, OH 45435
>
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>
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

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