[R] Population growthrate with Euler-Lotka
Simon Blomberg
s.blomberg1 at uq.edu.au
Mon Jun 30 12:41:34 CEST 2014
Your script is failing at the first hurdle because you data are not being imported properly. You should include
header=TRUE. sep=";"
In the call to read.table.
Cheers.
Simon.
Sent from my iPhone
Sent from my iPhone
> On 30 Jun 2014, at 7:10 pm, "Mark Christjani" <m_christjani at gmx.de> wrote:
>
>
> Hi everybody,
>
> I`m Mark and I do my PhD in biology. I try using R to calculate a population
> growth rate of animals grown on different types of food. Our workgroup has a
> R-skript to do so, but sadly nobody, who knows how this works. I`ve never
> used R before, but got some stuff figured out myself. The skript goes:
>
> setwd("c:/Mark")
> table <- read.table("r-TCO-Scene-Kontrolle.csv")
> table
> x <- c(table$x)
> L <- c(table$lx)
> m <- c(table$mx)
> r.range<- c(0, 5)
> eulerlotka <- function(r) sum(L * m * exp(-r * x)) - 1
> res <- uniroot(f = eulerlotka, interval = r.range, tol = 1e-8)
> res$root
>
> I understood that the first 3 lines are simply to load my data and show it
> in the workspace console. The next 4 lines define variables of my .csv table
> for R. Thus far, everything works fine. Now comes the Euler-Lotka equation,
> but somehow, this does not seem to work out as supposed. I tried to find a
> solution on the internet, but I think this formula is somewhat special so I
> could not find a suitible solution for my special problem. The console says:
>
>
>> setwd("c:/Mark")
>>
>> table <- read.table("r-TCO-Scene-Kontrolle.csv")
>>
>> table
> V1
> 1 x;lx;mx
> 2 1;1;0
> 3 2;1;0
> 4 3;1;0
> 5 4;1;0
> 6 5;1;0
> 7 6;1;0
> 8 7;1;0
> 9 8;1;0
> 10 9;1;0
> 11 10;1;0
> 12 11;0.2;3.5
>>
>> x <- c(table$x)
>> L <- c(table$lx)
>> m <- c(table$mx)
>> r.range<- c(0, 5)
>>
>> eulerlotka <- function(r) sum(L * m * exp(-r * x)) - 1
>> res <- uniroot(f = eulerlotka, interval = r.range, tol = 1e-8)
> Error in uniroot(f = eulerlotka, interval = r.range, tol = 1e-08) :
> f() values at end points not of opposite sign
>>
>> res$root
>
> Does anybody have an idea how to get this running?
>
> Thanks in advance
>
> Kind regards
> Mark
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