The very basics of making a plot in R

README.md

The very basics of making a plot using ggplot2 in R.

my-first-plot.R

# R has packages, which are bundles of code that add certain functionality. They
# can be installed from CRAN (a central repository) like so. We're going to
# install ggplot2 to make plots.
install.packages("ggplot2")

# To use a package, we have to load it:
library(ggplot2)

# Next we want some data. I have provided several files: sarna-2005.csv
# (population figures for American Jews) weber-1927.csv (data about Presbyterian
# churches in the United States) paulist-missions.geocoded.csv (missions by a
# Catholic missionary order) nhgis0011_ts_state.csv (population figures for US
# states over time)
#
# Let's load one of these into R. We do that with the function read.csv().
# (Don't worry about stringsAsFactors for now. This will save us headaches
# later.)
sarna <- read.csv("sarna-2005.csv", stringsAsFactors = FALSE)

# We can view what is in this data set by clicking the "environment" tab in R
# Studio. But we can also use built-in R functions.

# Just typing the name of the variable will show us what is inside it.
sarna

# What kind of value is our `sarna` variable?
class(sarna)

# It's a data frame, which you can think of as a spreadsheet for now. What are
# the values in the data frame? The `str()` function gives us the structure of
# the object. We can read about the `str()` function by reading the help:
?str

# Let's find the structure of `sarna`
str(sarna)

# Notice the list of variables are each preceded by `$`. The dollar sign let's
# us access the components of a data frame, i.e., the columns. (This is like the
# . in JavaScript.) Notice that we get a list of numbers in the column. R calls
# this a vector. (It's like an array.)
sarna$year
sarna$estimate.high

# Let's make a simple plot the estimate of the Jewish population in the United
# States. Our data will be `sarna`. Our x-axis will be year (time always goes on
# the x-axis). Our y-axis will be estimate.high. The `aes()` function tells ggplot which variables get mapped to which axis.
ggplot(data = sarna,
       aes(x = year, y = estimate.high)) +
  geom_point()

# Can you try these?
# 1. What if you replace `estimate.high` with `percentage.population.high`?
# 2. What if you replace `geom_point()` with geom_line()`?
# 3. What if you replace `geom_point()` with geom_bar(stat = "identity")`?
# 4. What happens if you add `+ ggtitle("My title here")`?
# 5. Can you load a different data set and make charts with it?

nhgis0011_ts_state.csv

paulist-missions.geocoded.csv

r-starter.Rproj

Version: 1.0

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SaveWorkspace: Default
AlwaysSaveHistory: Default

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UseSpacesForTab: Yes
NumSpacesForTab: 2
Encoding: UTF-8

RnwWeave: knitr
LaTeX: pdfLaTeX

AutoAppendNewline: Yes
StripTrailingWhitespace: Yes

sarna-2005.csv

weber-1927.csv