valiTrend: Some statistical checks on the printed results
In FoscoV/foreYield: forecasting yield result

It performs two validation. That the data provided for the regression are free from noticeable trends (which is very likely to be). Mainly it checks that the trend marked doesn't cause the data to have a worse fitting (MSE) than without any treatment. If it were such, then it notify this and prompts for a reset of Trends as marked previously.

1	valiTrend()

##---- Should be DIRECTLY executable !! ----
##-- ==>  Define data, use random,
##--	or do  help(data=index)  for the standard data sets.

## The function is currently defined as
function ()
{
    train <- subset(yieldPrev$due2trend, yieldPrev$due2trend$trended ==
        0)
    train <- merge(train, yieldPrev$actualYield, by = "YEAR")
    train$trended <- NULL
    train <- merge(train, yieldPrev$relatedModel, by = "YEAR")
    noTrendMod <- lm(as.formula(yieldPrev$model_formula), data = train)
    test <- subset(yieldPrev$due2trend, yieldPrev$due2trend$trended !=
        0)
    test <- merge(test, yieldPrev$relatedModel, by = "YEAR")
    test$trended <- NULL
    solution <- subset(yieldPrev$due2trend, yieldPrev$due2trend$trended !=
        0)
    solution <- merge(solution, yieldPrev$flatYield, by = "YEAR")
    solution$trended <- NULL
    woTrend <- predict(noTrendMod, newdata = test, se.fit = TRUE,
        type = "response", level = 0.95, interval = "prediction")
    predCfg <- merge(solution, yieldPrev$omniYield, by = "YEAR")
    predCfg$clean <- woTrend$fit[, 1]
    DnoTREND <- predCfg$YIELD - predCfg$pred
    DwTREND <- predCfg$OFFICIAL_YIELD - predCfg$clean
    sigNO <- sqrt(mean((DnoTREND - mean(DnoTREND))^2))
    sigW <- sqrt(mean((DwTREND - mean(DwTREND))^2))
    if (sigNO < sigW) {
        cat(c("NOTE that the pointed Trends are afflicted by some kind of problem, a BETTER FITting model can be obtained WITHout any TREND removal. \n"))
    }
    asimErr <- skewness(woTrend$fit[, 1] - solution$OFFICIAL_YIELD)
    predError <- woTrend$fit[, 1] - solution$OFFICIAL_YIELD
    sigma <- sqrt(mean((predError - mean(predError))^2))
    danger <- asimErr/sigma
    if (danger >= 2.6) {
        cat(c("\n ADVICE: \n The marked trend related dynamics don't fit with the data! \n "))
    }
    if (sigNO < sigW | danger >= 2.6) {
        cat(c("Do you want to reset the trend marked and proceed again? (y/n) \n"),
            fill = T)
        reBea <- scan(, what = "text", nmax = 1)
        while (reBea != "y" & reBea != "n") {
            cat("answer y or n")
            reBea <- scan(, what = "text", nmax = 1)
        }
        if (reBea == "y") {
            rm(list = c("breakPoint", "flatYield", "due2trend",
                "friendShip", "flattyn", "safeTrend", "yieldTrend",
                "flatOff", "tableXregression", "model_formula",
                "CVmsRes", "expYield", "omniYield", "modelLM",
                "PCmodel"), envir = yieldPrev)
            virgilio()
        }
    }
  }