# [R] help with population matrix

Roy Mendelssohn - NOAA Federal roy.mendelssohn at noaa.gov
Mon Feb 18 17:55:56 CET 2013

```See if this helps at all:

http://cran.r-project.org/web/packages/popbio/popbio.pdf

-Roy M.
On Feb 18, 2013, at 8:49 AM, John Kane <jrkrideau at inbox.com> wrote:

> Currently your code does not seem to make any sense
>
> John Kane
>
>
>> -----Original Message-----
>> From: sf62 at st-andrews.ac.uk
>> Sent: Mon, 18 Feb 2013 16:09:49 +0000
>> To: r-help at r-project.org
>> Subject: [R] help with population matrix
>>
>> Hi guys, I am a biologist and an R newbie, and I'm learning how to create
>> a
>> simple population model.
>>
>> So, I have a population matrix ("pop")of 30 age classes of female (1:4
>> are
>> non-breeders, 5:30 are breeders) which will be modelled for 100 years.
>>
>>> pop <- matrix(0,30,100)
>>
>> I then populate this matrix with 3 young adult females.
>>
>>> pop[5, 1] <- 3
>
> What is this expected to do?
>>
>> I then want to run this for 100 years, with stochasticity, to see how
>> this
>> population does over time.
>>
>>> for (y in 1:100)  {
>>>    pop[1,t+1] <- rbinom(1,colSums(pop[5:30, t]), b/2)
>>
>> (I haven't filled these in but you don't need them, they all have
>> different
>> survival probabilities to the sexually-mature adults.)
>>
>>>   pop[5, t+1] <- rbinom(1, pop[4, t], s2)
>>>   pop[6, t+1] <- rbinom(1, pop[5, t], s2)
>> .....
>>>   pop[30, t+1] <- rbinom(1, pop[29, t], s2)
>> }
>>
> What is t , s2 b etc?
>
>
>
>> So my question is: is there any way of populating this matrix without
>> having to explicitly write 30 lines of code? Because lines 5 - 30 are all
>> going to be the same, and yet even after 5 hours (literally) of web
>> searching and R manual reading I can't find a way to index the rows,
>> which
>> seems to be what's needed here.
>>
>> Any insight is welcome here, including a different way of modelling this
>> population.
>> Many thanks, Sam.
>
> This may be one of the cases where it really is better to have some detailed explanation of what you want rather than how to code it.
>
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**********************
"The contents of this message do not reflect any position of the U.S. Government or NOAA."
**********************
Roy Mendelssohn
Supervisory Operations Research Analyst
NOAA/NMFS
Environmental Research Division
Southwest Fisheries Science Center
1352 Lighthouse Avenue
Pacific Grove, CA 93950-2097

e-mail: Roy.Mendelssohn at noaa.gov (Note new e-mail address)
voice: (831)-648-9029
fax: (831)-648-8440
www: http://www.pfeg.noaa.gov/

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