Re: [R] a more elegant way to get percentages?

From: Dimitris Rizopoulos <dimitris.rizopoulos_at_med.kuleuven.be>
Date: Thu, 13 Mar 2008 16:02:55 +0100

well, check what the apply() gives for each row of 'x', i.e.,

x <- read.table(textConnection("locat val

1      a   5
2      b   5
3      b  15
4      c   5
5      c  20
6      c   5
7      c  10
8      d   5
9      d  15
10     d  10"), header = TRUE)

# apply() uses as.matrix() for data frames

# 1st row of 'x'
y <- as.matrix(x)[1, ]
x$val[x$locat == y]

# 2nd row of 'x'
y <- as.matrix(x)[2, ]
x$val[x$locat == y]

# 3rd row of 'x'
y <- as.matrix(x)[3, ]
x$val[x$locat == y]

# 4th row of 'x'
y <- as.matrix(x)[4, ]
x$val[x$locat == y]

in which 'y' is auto-replicated to match the length of 'x$locat' each time.

Best,
Dimitris



Dimitris Rizopoulos
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium

Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


> Now that people have answered Monica's query, can someone help me?!!
> See below.
>
> On 13-Mar-08 13:36:03, Monica Pisica wrote:
>>
>> Hi,
>>
>> I am trying to get percentages in a more elegant way. I have a
>> data.frame with locations and values (counts) of species at that
>> location. Each location is repeated for each species i have values
>> for
>> and i would like to get percentages of each species at that
>> location. I
>> am not sure if i am clear in my explanations so i will paste my
>> code
>> below:
>>
>>#####################
>>
>>> x
>> locat val
>> 1 a 5
>> 2 b 5
>> 3 b 15
>> 4 c 5
>> 5 c 20
>> 6 c 5
>> 7 c 10
>> 8 d 5
>> 9 d 15
>> 10 d 10
>
> With Monica's dataframe as above, the answer would be 100*x[,1]/z
> where we want z to be c(5,20,20,40,40,40,40,30,30,30).
>
> So, intending to give Monica a helpful answer, I tried
>
>> apply(x,1,function(y) sum(x[x[,1]==y,2]))
> 1 2 3 4 5 6 7 8 9 10
> 5 15 15 30 30 30 30 15 15 15
>
> and similarly
>
>> apply(x,1,function(y) sum(x$val[x$locat==y]))
> 1 2 3 4 5 6 7 8 9 10
> 5 15 15 30 30 30 30 15 15 15
>
>
> So why didn't this work? Where's my blind spot? Indeed, why
> did it gives the results it did?
>
> With thanks,
> Ted.
>
> --------------------------------------------------------------------
> E-Mail: (Ted Harding) <Ted.Harding_at_manchester.ac.uk>
> Fax-to-email: +44 (0)870 094 0861
> Date: 13-Mar-08 Time: 14:15:34
> ------------------------------ XFMail ------------------------------
>
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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Thu 13 Mar 2008 - 15:14:58 GMT

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