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7.9: Summary of important R code

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    33288
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    The main components of the R code used in this chapter follow with the components to modify in lighter and/or ALL CAPS text where y is a response variable, x is an explanatory variable, and the data are in DATASETNAME.

    • DATASETNAME %>% ggplot(mapping = aes(x = x, y = y)) + geom_point() + geom_smooth(method = “lm”)
      • Provides a scatter plot with a regression line.
      • Add + geom_smooth() to add a smoothing line to help detect nonlinear relationships.
    • MODELNAME <- lm(y ~ x, data = DATASETNAME)
      • Estimates a regression model using least squares.
    • summary(MODELNAME)
      • Provides parameter estimates and R-squared (used heavily in Chapter 8 as well).
    • par(mfrow = c(2, 2)); plot(MODELNAME)
      • Provides four regression diagnostic plots in one plot.
    • confint(MODELNAME, level = 0.95)
      • Provides 95% confidence intervals for the regression model coefficients.
      • Change level if you want other confidence levels.
    • plot(allEffects(MODELNAME))
      • Requires the effects package.
      • Provides a term-plot of the estimated regression line with 95% confidence interval for the mean.
    • DATASETNAME <- DATASETNAME %>% mutate(log.y = log(y)
      • Creates a transformed variable called log.y – change this to be more specific to your “\(y\)” or “\(x\)”.
    • predict(MODELNAME, se.fit = T)
      • Provides fitted values for all observed \(x\text{'s}\) with SEs for the mean.
    • predict(MODELNAME, newdata = tibble(x = XNEW), interval = “confidence”)
      • Provides fitted value for a specific \(x\) (XNEW) with CI for the mean. Replace x with name of explanatory variable.
    • predict(MODELNAME, newdata = tibble(x = XNEW), interval = “prediction”)
      • Provides fitted value for a specific \(x\) (XNEW) with PI for a new observation. Replace x with name of explanatory variable.
    • qt(0.975, df = n - 2)
      • Gets the \(t^*\) multiplier for making a 95% confidence or prediction interval with \(n-2\) replaced by the sample size – 2.

    This page titled 7.9: Summary of important R code is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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