Plot better interaction plots for QGAMs — better_interaction

better_interaction_plot creates either a smooth plot with confidence intervals (for numeric:factor interactions) or a point plot with confidence interval ranges (for factor:factor interactions) using ggplot2. The underlying functions are similar to better_parametric_plot and better_smooth_plot.

better_interaction_plot(
  qgam,
  quantile = NULL,
  pred,
  cond,
  order,
  ncol = 1,
  type,
  xlab = NULL,
  ylab = NULL,
  scales = NULL,
  size = 0.5,
  fill = NULL,
  color = NULL,
  alpha = 1,
  names = NULL)

Arguments

qgam: A qgam object created with qgam::qgam or extracted from a qgam::mqgam object, or a collection of qgams created with qgam::mqgam.
quantile: If qgam is a collection of qgam models, specify the quantile you are interested in. Not meaningful for single qgam objects.
pred: The predictor you wish to plot. Must be one of the predictor or smooth terms given in the qgam formula.
cond: The predictor pred is in interaction with.
order: Specify the order with which the levels given in pred should be plotted. This is only meaningful for interaction plots of factors.
ncol: The number of columns of the multi-panel plot. This is not meaningful for type = "no_facet" plots.
type: For interaction plots of two numeric variables, choose either "facet" (the default) or "no_facet". This is only meaningful for interaction plots of numeric variables.
xlab: The x-axis label.
ylab: The y-axis label.
scales: Should scales be fixed ("fixed", the default) or free ("free")? This is not meaningful for type = "no_facet" plots.
size: Size argument for the ggplot object; specifies the size of the line / the size of the point and whiskers.
fill: Color argument for the ggplot object; specifies the color of the confidence interval. This is only meaningful for interaction plots of numeric variables.
color: Color argument for the ggplot object; specifies the color of the lines and dots. For interaction plots of factors, this must be a vector of colors with a length equal to the combinations of factor levels. For interaction plots of numeric variables and factors, this is a single color.
alpha: Alpha argument for the ggplot object; specifies the transparency of the confidence interval for interaction plots of numeric variables, and specifies the transparency of point and whiskers for interaction plots of interaction plots for factors. The value of alpha is changed to 0.5 by default for no_facet plots.
names: Strings used as facet labels.

Value

A ggplot object.

References

Fasiolo M., Goude Y., Nedellec R., & Wood S. N. (2017). Fast calibrated additive quantile regression. URL: https://arxiv.org/abs/1707.03307

van Rij J, Wieling M, Baayen R, & van Rijn H (2020). itsadug: Interpreting Time Series and Autocorrelated Data Using GAMMs. R package version 2.4.

Wickham, H. (2016). ggplot2: Elegant Graphics for Data Analysis. Springer-Verlag New York.

Author

D. Schmitz

Examples


### examples for factor:factor interactions

# using a single qgam extracted from an mqgam object OR fitted with qgam::qgam
better_interaction_plot(qgam = mtqgam_qgam,
  pred = "factor_3",
  cond = "factor_2")
#> Loading required package: ggplot2


# using a qgam that is part of an mqgam object
better_interaction_plot(qgam = mtqgam_mqgam,
  quantile = 0.5,
  pred = "factor_3",
  cond = "factor_2")


# specifying color
better_interaction_plot(qgam = mtqgam_qgam,
  pred = "factor_3",
  cond = "factor_2",
  color = c("blue", "purple"))


# specifying facet labels
better_interaction_plot(qgam = mtqgam_qgam,
  pred = "factor_2",
  cond = "factor_3",
  names = c("facet A", "2nd facet"))


# combining better_interaction_plot with ggplot2
better_interaction_plot(qgam = mtqgam_qgam,
  pred = "factor_3",
  cond = "factor_2") +
  theme_void() +
  labs(subtitle = "This is a subtitle")


### examples for numeric:factor interactions

# using a single qgam extracted from an mqgam object OR fitted with qgam::qgam
better_interaction_plot(qgam = mtqgam_qgam,
  pred = "numeric_2",
  cond = "factor_1")
#> Error in facet_names[[a]] <- label: attempt to select less than one element in integerOneIndex

better_interaction_plot(qgam = mtqgam_qgam,
  pred = "numeric_2",
  cond = "factor_1",
  type = "no_facet")
#> ! The ncol argument is not meaningful for no_facet interaction plots of smooth terms. Plotting anyway.
#> ! Changing alpha to 0.5 for better legibility.


# specifying color
better_interaction_plot(qgam = mtqgam_qgam,
  pred = "numeric_2",
  cond = "factor_1",
  color = "blue", "purple")
#> ! The quantile argument is not meaningful for single QGAM objects. Plotting anyway.
#> Error in facet_names[[a]] <- label: attempt to select less than one element in integerOneIndex

# using a qgam that is part of an mqgam object
better_interaction_plot(qgam = mtqgam_mqgam,
  quantile = 0.5,
  pred = "numeric_2",
  cond = "factor_1")
#> Error in facet_names[[a]] <- label: attempt to select less than one element in integerOneIndex

# combining better_interaction_plot with ggplot2
better_interaction_plot(qgam = mtqgam_qgam,
  pred = "numeric_2",
  cond = "factor_1") +
  theme_void() +
  labs(subtitle = "This is a subtitle")
#> Error in facet_names[[a]] <- label: attempt to select less than one element in integerOneIndex