On 1/28/19 4:00 PM, Alan Feuerbacher wrote:
On 1/28/2019 4:20 PM, Rolf Turner wrote:

On 1/29/19 10:05 AM, Alan Feuerbacher wrote:

Hi,

I recently learned of the existence of R through a physicist friend who uses it in his research. I've used Octave for a decade, and C for 35 years, but would like to learn R. These all have advantages and disadvantages for certain tasks, but as I'm new to R I hardly know how to evaluate them. Any suggestions?
>
snpped
* The syntax of R meshes beautifully with *my* thought patterns; YMMV.

* Why not just bog in and try R out?  It's free, it's readily available,
   and there are a number of good online tutorials.

I just installed R on my Linux Fedora system, so I'll do that.

I wonder if you'd care to comment on my little project that prompted this? As part of another project, I wanted to model population growth starting from a handful of starting individuals. This is exponential in the long run, of course, but I wanted to see how a few basic parameters affected the outcome. Using Octave, I modeled a single person as a "cell", which in Octave has a good deal of overhead. The program basically looped over the entire population, and updated each person according to the parameters, which included random statistical variations. So when the total population reached, say 10,000, and an update time of 1 day, the program had to execute 10,000 x 365 update operations for each year of growth. For large populations, say 100,000, the program did not return even after 24 hours of run time.

So I switched to C, and used its "struct" declaration and an array of structs to model the population. This allowed the program to complete in under a minute as opposed to 24 hours+. So in line with your comments, C is far more efficient than Octave.

How do you think R would fare in this simulation?

This sounds like a problem that would fit into a stochastic differential equation.  There are at least three packages in CRAN (and I suspect a few more) that will handle simulations of stochastic differential equations. Bert's suggestion to use Rseek should serve you well.


--

David.

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