# [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

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
>   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
>              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?
>