[R] accessing variables inside a function, inside a loop

[jim holtman]

A quick look says you are passing N_Male in which is a vector of
values, but you are trying to use it as if it were a character value
in:

y <- DATA[[y]]

try calling it with

comp.plot(i,"N_male",DATA=water)

Also get out of the habit of using 'attach'; it can lead to other issues.

On Sun, Feb 27, 2011 at 3:48 PM, Sacha Viquerat <tweedie-d at web.de> wrote:
> dear list!
> I KNOW this has been answered a million times before. But, as some might
> remember from their "freelance" times as a statistic consultant, sometimes
> you're blinded by the facts. I KNOW I have seen this problem solved, but due
> to the mental blockade i have been suffering from the last 3 hours, I can
> neither find the answer on the mailing list nor on google. I wrote a
> function to plot one continuous variable against an abundance of fish, the
> data is called water. however, my data covers 9 parameters, and since I am
> lazy as hell, I decided to write a for loop to pass all the variables to the
> function. as usual, the variables and the data frame cannot be found inside
> the function.
>
> water<-read.csv("Henni/water-abundance2.csv",sep="\t",header=T)
> source("functions.R")
> attach(water)
>
> names(water):
>  [1] "site"     "sample"   "temp"     "pH"       "DO"       "BOD"
>  [7] "COD"      "no3"      "no2"      "po4"      "N_male"   "N_female"
>
> vars<-names(water)[3:10]
>
> par(mfrow=c(4,2))
> for (i in vars)
> {
>    comp.plot(i,N_male,DATA=water)
> }
>
> comp.plot<-function(parameter,y,DATA){ #this is actually in functions.R
>    x<-DATA[[parameter]]
>    y<-DATA[[y]]
>    plot(y~parameter)
> }
>
> and of course, this doesn't work. I am really frustrated by now, since I
> have gathered all I could recollect from my past 2 years of R experience but
> still, I was not able to find a solution. I'm really dizzy right now, but
> since I will not be able to go to sleep unless I have found the answer to
> this problem, I urge someone to shed some light on my trivial problem! I
> will promise not to post this question ever again, but for now, I'm just
> stuck!
>
> Thanks in advance and humble apologies to all that feel offended by my post!
>
> ______________________________________________
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?