two_way_anova {kim}

Two-way ANOVA

Description

Conduct a two-way analysis of variance (ANOVA).

Usage

two_way_anova(
  data = NULL,
  dv_name = NULL,
  iv_1_name = NULL,
  iv_2_name = NULL,
  iv_1_values = NULL,
  iv_2_values = NULL,
  sigfigs = 3,
  robust = FALSE,
  iterations = 2000,
  plot = TRUE,
  error_bar = "ci",
  error_bar_range = 0.95,
  error_bar_tip_width = 0.13,
  error_bar_thickness = 1,
  error_bar_caption = TRUE,
  line_colors = NULL,
  line_types = NULL,
  line_thickness = 1,
  dot_size = 3,
  position_dodge = 0.13,
  x_axis_title = NULL,
  y_axis_title = NULL,
  y_axis_title_vjust = 0.85,
  legend_title = NULL,
  legend_position = "right",
  output = "anova_table",
  png_name = NULL,
  width = 7000,
  height = 4000,
  units = "px",
  res = 300,
  layout_matrix = NULL
)

Arguments

data

a data object (a data frame or a data.table)

dv_name

name of the dependent variable

iv_1_name

name of the first independent variable

iv_2_name

name of the second independent variable

iv_1_values

restrict all analyses to observations having these values for the first independent variable

iv_2_values

restrict all analyses to observations having these values for the second independent variable

sigfigs

number of significant digits to which to round values in anova table (default = 3)

robust

if TRUE, conduct a robust ANOVA in addition.

iterations

number of bootstrap samples for robust ANOVA. The default is set at 2000, but consider increasing the number of samples to 5000, 10000, or an even larger number, if slower handling time is not an issue.

plot

if TRUE, print a plot and enable returning an output (default = TRUE)

error_bar

if error_bar = "se"; error bars will be +/-1 standard error; if error_bar = "ci" error bars will be a confidence interval

error_bar_range

width of the confidence interval (default = 0.95 for 95 percent confidence interval). This argument will not apply when error_bar = "se"

error_bar_tip_width

graphically, width of the segments at the end of error bars (default = 0.13)

error_bar_thickness

thickness of the error bars (default = 1)

error_bar_caption

should a caption be included to indicate the width of the error bars? (default = TRUE).

line_colors

colors of the lines connecting means (default = NULL) If the second IV has two levels, then by default, line_colors = c("red", "blue")

line_types

types of the lines connecting means (default = NULL) If the second IV has two levels, then by default, line_types = c("solid", "dashed")

line_thickness

thickness of the lines connecting group means, (default = 1)

dot_size

size of the dots indicating group means (default = 3)

position_dodge

by how much should the group means and error bars be horizontally offset from each other so as not to overlap? (default = 0.13)

x_axis_title

a character string for the x-axis title. If no input is entered, then, by default, the first value of iv_name will be used as the x-axis title.

y_axis_title

a character string for the y-axis title. If no input is entered, then, by default, dv_name will be used as the y-axis title.

y_axis_title_vjust

position of the y axis title (default = 0.85). By default, y_axis_title_vjust = 0.85, which means that the y axis title will be positioned at 85% of the way up from the bottom of the plot.

legend_title

a character for the legend title. If no input is entered, then, by default, the second value of iv_name will be used as the legend title. If legend_title = FALSE, then the legend title will be removed.

legend_position

position of the legend: "none", "top", "right", "bottom", "left", "none" (default = "right")

output

output type can be one of the following: "anova_table", "group_stats", "plot", "robust_anova_results", "robust_anova_post_hoc_results", "robust_anova_post_hoc_contrast", "all"

png_name

name of the PNG file to be saved. If png_name = TRUE, the name will be "two_way_anova_" followed by a timestamp of the current time. The timestamp will be in the format, jan_01_2021_1300_10_000001, where "jan_01_2021" would indicate January 01, 2021; 1300 would indicate 13:00 (i.e., 1 PM); and 10_000001 would indicate 10.000001 seconds after the hour.

width

width of the PNG file (default = 7000)

height

height of the PNG file (default = 4000)

units

the units for the width and height arguments. Can be "px" (pixels), "in" (inches), "cm", or "mm". By default, units = "px".

res

The nominal resolution in ppi which will be recorded in the png file, if a positive integer. Used for units other than the default. If not specified, taken as 300 ppi to set the size of text and line widths.

layout_matrix

The layout argument for arranging plots and tables using the grid.arrange function.

Details

The following package(s) must be installed prior to running this function: Package 'car' v3.0.9 (or possibly a higher version) by Fox et al. (2020), https://cran.r-project.org/package=car

If robust ANOVA is to be conducted, the following package(s) must be installed prior to running the function: Package 'WRS2' v1.1-1 (or possibly a higher version) by Mair & Wilcox (2021), https://cran.r-project.org/package=WRS2

Value

by default, the output will be "anova_table"

Examples

two_way_anova(
  data = mtcars, dv_name = "mpg", iv_1_name = "vs",
  iv_2_name = "am", iterations = 100)
anova_results <- two_way_anova(
  data = mtcars, dv_name = "mpg", iv_1_name = "vs",
  iv_2_name = "am", output = "all")
anova_results