On 19-03-2012, at 12:42, Letnichev wrote: > Hello everyone, > > I am working for a few days already on a basic algorithm, very common in > applied agronomy, that aims to determine the degree-days necessary for a > given individual to reach a given growth stade. The algorithm (and context) > is explained here: http://www.oardc.ohio-state.edu/gdd/glossary.htm , and > so I implemented my function in R as follows: > > DD <- function(Tmin, Tmax, Tseuil, meanT, method = "DDsin") > ### function that calculates the degree-days based on > ### minimum and maximum recorded temperatures and the > ### minimal threshold temperature (lower growth temperature) > { > ### method arcsin > if(method == "DDsin"){ > cond1 <- (Tmax <= Tseuil) > cond2 <- (Tmin >= Tseuil) > amp <- ((Tmax - Tmin) / 2) > print((Tseuil-meanT)/amp) > alpha <- asin((Tseuil - meanT) / amp) > DD_ifelse3 <- ((1 / pi) * ((meanT - Tseuil) * ((pi/2) - alpha)) > + > amp*cos(alpha)) > > DD <- ifelse(cond1, 0, ifelse(cond2, (meanT - Tseuil), > DD_ifelse3)) > } > > ### method (Tmin + Tmax) / 2 > else if(method == "DDt2"){ > cond1 <- (meanT > Tseuil) > DD <- ifelse(cond1,(meanT - Tseuil),0) > } > > else{ > stop("\nMethod name is invalid.\nMethods available = DDsin > (sinus) or DDt2 > (mean)\n") > } > return(DD) > } > > BUT! When I try to process random data: > > library(reshape2) > library(plyr) > > station <- rep(c("station1","station2","station3"), 20) > values_min <- sample(-5:20, size = 60, replace = T) > values_max <- sample(20:40, size = 60, replace = T) > meanT <- ((values_min+values_max)/2) > d <- data.frame(station,values_min,values_max,meanT) > names(d) <- c("station", "values_min","values_max","meanT") > > x<-ddply(d, .(station), transform, t1 = > cumsum(DD(values_min,values_max,0,meanT))) > > I get a warning on my alpha calculation (NaN produced); indeed, the values I > give as argument to asin() are out of the range [-1:1], as the print() > reveals. I can't figure out how to solve this issue, because the same > algorithm works in Excel (visual basic).
That doesn't mean that Excel and/or Visual Basic gives correct answers. With the same input? Then what does Excel say that asin(-7.4) evaluates to? I tried asin(-1.2) and asin(-7.4) in LibreOffice Calc (3.5.0) and got #VALUE! (Error: wrong data type) twice. You'll have to present correct input to asin() if you want to avoid the NaN's. Berend > It is very annoying, especially because it seems that no occurence of such > error using that algorithm can be found on Internet. > Any help is welcome :) Thanks for your time > > P. > > -- > View this message in context: > http://r.789695.n4.nabble.com/Issue-with-asin-tp4484462p4484462.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
