# [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?
>