Importing a CSV file
data <- read.csv("file.csv")
Use when
Use when loading a spreadsheet-style data file into RStudio.
Output means
Creates a data frame called data.
Example
survey <- read.csv("survey.csv")
Back to RStudio and Project Skills
Higher Applications of Mathematics
RStudio reference
Quick reference cards for common RStudio commands, when to use them, and how to interpret the output.
Checking column names
names(data)
Use when
Use after importing data to check exact variable names.
Output means
Lists the column names you can use in commands.
Example
names(survey)
Summary statistics
mean(x), median(x), sd(x), summary(x)
Use when
Use to describe centre, spread and range.
Output means
Gives numerical summaries for a variable.
Example
mean(survey$height)
Box plots
boxplot(x)
Use when
Use to compare spread, median and possible outliers.
Output means
Shows median, quartiles, range and outliers.
Example
boxplot(survey$travel_time)
Histograms
hist(x)
Use when
Use to show the shape of a numerical distribution.
Output means
Shows frequencies in grouped intervals.
Example
hist(survey$screen_time)
Scatter plots
plot(x, y)
Use when
Use to show the relationship between two numerical variables.
Output means
Each point represents one pair of values.
Example
plot(survey$revision, survey$score)
Correlation
cor(x, y)
Use when
Use to measure strength and direction of a linear relationship.
Output means
Returns a value between -1 and 1.
Example
cor(survey$revision, survey$score)
Linear regression
model <- lm(y ~ x, data = data)
Use when
Use to fit a straight-line model and make predictions.
Output means
Gives intercept, gradient and model summary.
Example
lm(score ~ revision, data = survey)
Confidence intervals
t.test(x)$conf.int
Use when
Use to estimate a population mean from sample data.
Output means
Gives a plausible interval for the true mean.
Example
t.test(survey$height)$conf.int
One-sample t-test
t.test(x, mu = value)
Use when
Use to test whether a sample mean differs from a claimed mean.
Output means
Use the p-value to judge evidence against the claim.
Example
t.test(times, mu = 30)
Paired t-test
t.test(before, after, paired = TRUE)
Use when
Use when the same people are measured twice.
Output means
Tests whether the mean paired difference is 0.
Example
t.test(before, after, paired = TRUE)
Two-proportion test
prop.test(c(success1, success2), c(total1, total2))
Use when
Use to compare two sample proportions.
Output means
Gives a p-value for evidence of a difference in proportions.
Example
prop.test(c(42, 55), c(100, 120))
Exporting or saving results
write.csv(results, "results.csv")
Use when
Use when saving a table for a project write-up.
Output means
Creates a CSV file from an R object.
Example
write.csv(summary_table, "summary.csv")
Common RStudio errors
Check spelling, capitals, brackets and data names
Use when
Use when R says an object is not found or a command fails.
Output means
Most early errors come from mistyped names or missing brackets.
Example
survey$Height is different from survey$height.