USGS - science for a changing world

Crib Sheet

Function/operator Description Package (if not base R) Lesson Introduced
# my comment Comment A
myfunction() Function call A
mydata[1,4] Indexing [row, col] A
{ my...code } Code block (function definitions, etc.) A
install.packages Install a package (like installing a software program) A
library Load a package (like opening a program) A
mylib::myfun() Call the version of the function myfun that's defined in the library mylib A
help("print") Get the help page for a topic A
?print Get the help page for a topic A
apropos("print") Search help topics containing "print" A
??"print" Search help topics containing "print" A
ls("package:stats") List the functions defined in the stats package A
pri - Tab When you press the Tab key, RStudio tries to complete your word A
1+1 Add B
10-4 Subtract B
3*2 Multiply B
3^3 Exponents B
100/10 Divide B
5%%2 Modulus B
5>2 Greater than B
4<5 Less than B
5<=5 Less than or equal B
8>=2 Greater than or equal B
2==2 Equality B
5!=7 Not Equals B
x <- 8 Assignment operator B
z <- 8 + x B
a <- "R Class" B
print(x) Print objects or values in the console B
x B
ls() List objects in the current workspace B
rm(x) Remove an object B
getwd() See what file directory your workspace is currently set to B
setwd() Change the working directory -- be careful with this! B
list.files() See the names of files in your current directory B
is.na() Says whether a value(s) is missing (NA) or not B
na.omit() Removes an missing (NA) values B
c() Combine arguments into a vector (or combine lists) B
class() Tells you the R data type B
str() Says the class and gives a small summary B
length() Gives the number of elements B
seq() Create a series of numbers (or dates) B
1:10 B
rep() Repeat individual values, vectors, or lists B
paste() Combine multiple character strings B
factor() Create factors from character or numeric vectors B
data.frame() Create a data frame, don't forget this is a default arg: stringsAsFactors = TRUE B
head() Look at the top 6 rows of a data frame (unless n is specified) B
tail() Look at the bottom 6 rows of a data frame (unless n is specified) B
names() Get the names of an R object B
colnames() Get column names of data frame B
rownames() Get row names of data frame B
dim() Tells the number of rows and/or columns in a data frame B
nrow() B
ncol() B
summary() Summarizes each column of a data frame, gives basic stats for numeric columns B
list() Create lists B
read.csv() Load data into R from a filepath or URL B
read.table() B
write.csv() Save R objects as files B
write.table() B
readNWISdata() Read in data from NWIS dataRetrieval B
readNWISqw() Read in water quality data from NWIS dataRetrieval B
x[7] Get the seventh element of a vector C
x[8:10] Get a elements from index 8 though 10 C
x[c(2, 3, 5)] Get elements 2, 3, and 5 C
x[c(TRUE, FALSE)] Subset with logicals C
x[x %% 2 == 0] Example of subsetting with a "filter" C
select() Select columns out of a data frame dplyr C
filter() Filter data based on some condition dplyr C
rbind() Combine two R objects either row- or column-wise C
merge() Merge two data frames on a column C
all.equal() Test if two objects are equal C
inner_join() Inner join between two data frames dplyr C
left_join() Left outer join between two data frames dplyr C
right_join() Right outer join between two data frames dplyr C
full_join() Full outer join between two data frames dplyr C
anti_join() Drop all rows in the first data frame that has a match in the second dplyr C
group() Group data by a specified column in a data frame dplyr C
summarize() Summarize multiple values into a single value dplyr C
arrange() Arrange rows by variables. Defaults to ascending order dplyr C
slice() Slice an object dplyr C
mutate() Create a new column based on some operation on an existing column dplyr C
rowwise() Apply some operation to each row dplyr C
range() Find the range of a vector D
IQR() Get the interquartile range of a vector D
quantile() Defaults to 0, 25, 50, 75, and 100% quantiles of a vector D
plot() Basic function for creating scatterplots, can also take data frames as inputs D
abline() Add a line to a plot using slope + y-intercept,vertical or horizontal value, or a linear model D
lm() Find the regression line for a dataset D
boxplot() Create boxplots D
hist() Create histograms D
ecdf() Empirical cumulative distribution (can be used as an input to plot() ) D
t.test() t-test E
cor() Correlation (several methods available) E
cor.test() Correlation test E
lm() Linear regression model E
summary(lm()) Summarize a linear regression model E
readNWISDaily() Get NWIS daily data EGRET F
readNWISInfo() Get NWIS site information EGRET F
as.egret() Create an EGRET data object EGRET F
plotFlowSingle() Make a 1-panel plot of flow EGRET F
setPA() Set the period of analysis for a WRTDS model EGRET F
plotFourStats() Plot mean, max, median, and 7-day minimum stats for discharge EGRET F
readNWISSample() Get NWIS sample data EGRET F
mergeReport() Combine EGRET data objects EGRET F
multiPlotDataOverview() Inspect solute data in 4 plots EGRET F
modelEstimation() Fit a WRTDS model EGRET F
vignette() Run a vignette or list the vignettes in a package F
plot() Make a basic plot G
points() Add points to a plot G
par() Set plotting parameters G
par(las=) Set axis label orientation G
par(tck=) Set tick length G
par(bg=) Set background color G
legend() Add a legend to a plot G
curve() Plot an expression G
rect() Add a rectangle to a plot G
polygon() Add a polygon to a plot G
symbols() Add symbols to a plot G
axis() Add tick marks and labels to an axis G
layout() Specify a layout for multiple plots on a figure G
png() Open a .png plotting device G
svg() Open an .svg plotting device G
jpeg() Open a .jpeg plotting device G
pdf() Open a .pdf plotting device G
dev.off() Save and close one or more plotting devices G
ggplot() Start a plot ggplot2 H
ggplot(aes()) Set the aesthetics (variables for x, y, groups, colors, etc.) for a plot ggplot2 H
g + geom_point() Add points to a plot ggplot2 H
labs() Set main and axis labels for a plot ggplot2 H
ggtitle() Set the main title of a plot ggplot2 H
xlab() Set the x axis label for a plot ggplot2 H
ylab() Set the y axis label for a plot ggplot2 H
geom_smooth() Add a smoother or regression line to a plot ggplot2 H
geom_boxplot() Add boxes to a plot ggplot2 H
geom_histogram() Add a histogram to a plot ggplot2 H
geom_bar() Add bars to a plot ggplot2 H
theme() Set thematic traits of a plot ggplot2 H
theme_bw() A simple black and white plot theme ggplot2 H
theme_classic() A very simple black and white plot theme ggplot2 H
ggsave() Save a ggplot ggplot2 H
function() Define a function I
if Conditional control structure I
ifelse Conditional control structure I
else Conditional control structure I
for Control structure for a loop I
system.time() Return CPU time I
return() Include in a function to reply with a specific value to the caller I
jitter() Add some random noise to a numeric vector I

Lindsay R. Carr