Building Blocks
What code would initialize a plot made from the mtcars dataset data set where hp (horsepower) is on the X axis and mpg (miles per gallon) is on the Y axis?
ggplot(mtcars, aes(x = hp, y = mpg))
What role do aesthetic mappings play in the creation of a ggplot?
Aesthetic mappings determine how values are assigned to the visual aspects of your plot.
What would the plot generated by the code below look like?
ggplot(iris, aes(y = Sepal.Width))
A blank plot with nothing but a Y axis.
What shorthand function (and the argument) could I use to add the caption "my caption" to my plot?
labs(caption = "my caption")
What code can I add to my plot to replicate the plot once for each value of e.g., a hair_color variable?
facet_wrap(facets = hair_color)
Which building block of ggplot - and the two subtypes - determines which type of plot will be drawn?
Layers
Two subtypes: geoms and stats
What is the difference between the color and fill aesthetics?
Color affects the colors of lines and points (for example, the colors of the borders around bars on a bar plot), while fill affects the color of white spaces (for example, the color of the area insides of bars on a bar plot).
Add the code to the code below that would make a dashed trend line:
geom_smooth()
geom_smooth(linetype = "dashed")
What determines the location of each aspect of a ggplot?
the coordinate system
What do the arguments of the theme function represent?
Each customizable aspect of your plot.
What does the facet_wrap function do?
Replicates the plot once for each unique value of another variable.
What is the difference between setting an aesthetic inside the aes() function vs setting it outside the aes() function but inside of a geom?
Inside of the aes() function, the aesthetic will be set to a variable, whereas outside of the function but inside a geom, it will be set to a user–specified value (e.g. a color).
What is the difference between a global versus local aesthetic?
Global aesthetics apply to the entire plot, whereas local aesthetics apply only to the specific geom they are used in.
Say that I wanted to plot the square root of a continuous variable located on the Y axis. What function could I use?
scale_y_continuous()
Which element function does the background of a plot go with?
element_rect()
What are the two ways that I can change the superficial appearance of my plot?
By adding one of the built-in themes or by manually cuctomizing specific aspects of the plot with the theme() function.
What would the following argument do to my bar plot:
aes(x = species, y = mass, color = gender)
It would make the color of points and/or lines in the plot depend on the gender variable.
What aesthetic would make the color of the inside of all of my violin plots pink? Note: must specify the location of the argument ;)
fill = "pink" (outside of the aes() function, inside of the geom, or geom_violin() in this case).
When using geom_bar() with a continuous variable on the Y axis, what is the argument that makes the top of each bar equal to the mean of that variable?
stat = "summary"
Name an aspect of a ggplot that corresponds to the element_text() function used by theme().
Some possibilities...
- plot.title
- plot.caption
- axis.title.x/asxis.title.y
- axis.text.x/axis.text.y
- legend.text
Say I want to manually change the fill of the bars on my bar chart. Which function could I add to my ggplot to do that?
scale_fill_manual()
What is the difference between a plots aesthetics and its scales?
Aesthetics assign variables to different aspects of the plots, and scales do the work of actually drawing each aspect of the plot.
Say I wanted to make a scatter plot where the size of the points depends on the value of the pedal dark length variable. What would the argument and its setting be? Note: the location of the argument must be specified ;)
size = Pedal.Length (inside of the aes() function).
When using geom_histogram(), which only accepts an aesthetic mapping for the X axis (but not the Y axis), what role is the step function playing in creating this plot?
It is calculating the count variable that is displayed on the way access.
If I want to change the horizontal and vertical position of something on my plot along the coordinate system, which arguments would I use (e.g., inside of one of the element functions)?
hjust and vjust (which stand for horizontal justification and vertical justification, respectively).