C++ based chill portion calculator for R
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C++ based chill portion calculator

Itai Trilnick, July 25th 2018

This package has a C++ implementation for calculating chill portions, an important metric in agronomy. It is specially used for bloom prediction in fruit trees. The chill portion calculation is sequential, based on a vector of temperatures. Temperatures need to stay within a certain range for a certain time for a chill portion to "bank". Therefore, this function cannot be vectorized. Alas, loops are incredibly slow in R, and I needed to do this many times, so I transformed my existing R code to C++ and added this functionality with Rcpp (thanks, Hadley!).

The function is based on a spreadsheet, distributed by Fishman et al based on their 1987 paper. There is a comprehensive R package for dealing with chill, chillR, which also has a function for chill portion calculations (function chilling). The package seems to be well written, and I have been using some of its functions. However, the chilling function requires a data-frame input which I found less convenient for my work, and is coded as an R loop.

At this point, I do not intend to publish this mini package on CRAN. You can download it with devtools::install.github('trilnick/miniChill'). I noticed that, even though the compiled files are already in the repository, R will try to compile it on its own, and for this you will need Rtools installed. Therefore, I also uploaded miniChill_1.0.zip, a binary package compiled on a Windows machine, which you can download and install without Rtools.

I'm happy to get feedback on this function. Send me an email or post an issue here on Github!