R/rice.R

In ipsRdbs: Introduction to Probability, Statistics and R for Data-Based Sciences

#' Riece yield data 
#' 
#' @source \insertCite{BAL1975353;textual}{ipsRdbs}.  
#' @format A data frame with three columns and 68 rows:
#' \describe{
#'   \item{Yield}{Yield of rice in kilograms}
#'   \item{Days}{Number of days after flowering before harvesting}
#' }
#' @examples
#'  summary(rice)
#'  plot(rice$Days, rice$Yield, pch="*", xlab="Days", ylab="Yield")
#'  rice$daymin31 <- rice$Days-31
#'  rice.lm <- lm(Yield ~ daymin31, data=rice)
#'  summary(rice.lm)
#'  # Check the diagnostics 
#'  plot(rice.lm$fit, rice.lm$res, xlab="Fitted values", ylab = "Residuals")
#'  abline(h=0)
#'  # Should be a random scatter
#'  # Needs a quadratic term
#'  
#'  qqnorm(rice.lm$res, col=2)
#'  qqline(rice.lm$res, col="blue")
#'  rice.lm2 <- lm(Yield ~ daymin31 + I(daymin31^2) , data=rice)
#'  old.par <- par(no.readonly = TRUE)
#'  par(mfrow=c(1, 2))
#'  plot(rice.lm2$fit, rice.lm2$res, xlab="Fitted values", ylab = "Residuals")
#'  abline(h=0)
#'  # Should be a random scatter 
#'  # Much better plot!
#'  qqnorm(rice.lm2$res, col=2)
#'  qqline(rice.lm2$res, col="blue")
#'  summary(rice.lm2)
#'  par(old.par) # par(mfrow=c(1,1))
#'  plot(rice$Days,  rice$Yield, xlab="Days", ylab="Yield")
#'  lines(rice$Days, rice.lm2$fit, lty=1, col=3)
#'  rice.lm3 <- lm(Yield ~ daymin31 + I(daymin31^2)+I(daymin31^3) , data=rice)
#'  #check the diagnostics 
#'  summary(rice.lm3) # Will print the summary of the fitted model 
#'  #### Predict at a new value of Days=31.1465
#'  
#'  # Create a new data set called new
#'  new <- data.frame(daymin31=32.1465-31)
#'  
#'  a <- predict(rice.lm2, newdata=new, se.fit=TRUE) 
#'  # Confidence interval for the mean of rice yield  at day=31.1465
#'  a <- predict(rice.lm2, newdata=new, interval="confidence") 
#'  a
#'  #          fit      lwr      upr
#'  # [1,] 3676.766 3511.904 3841.628
#'  # Prediction interval for a future yield at day=31.1465
#'  b <- predict(rice.lm2, newdata=new, interval="prediction") 
#'  b
#'  # fit      lwr      upr
#'  #[1,] 3676.766 3206.461 4147.071
"rice"