R: Brief Reference Page |
| command | function | notes/examples |
| Miscellaneous | ||
| q( ) | quit R | |
| <- | assignment | x <- 17 |
| = | assignment | x = 17 |
| help( ) | ask for help | help(q) or ?q: help on the quit function |
| help.start( ) | help browser | |
| data( ) | R internal datasets | data(co2): atmospheric co2 dataset |
| Managing Data | ||
| ls( ) | list objects in workspace | ls(pat="^O"): list objects beginning with "O" ls(pat="O") : list object names including an "O" |
| rm( ) | remove objects from workspace | rm("X") |
| attach(DF) | add the data frame DF to search list | |
| detach(DF) | remove data frame DF from search list | |
| dim(DF) | dimensions of matrix or dataframe DF | |
| names(DF) | column names of dataframe DF | |
| dimnames(DF) | row and column names of DF | |
| DF[1, ] | first row of DF | |
| DF[ ,2] | second column of DF | |
| DF[ ,"X"] | column of DF named "X" | |
| length(x) | length of the vector x | |
| sort( ) | sort a dataset | default is ascending order |
| factor( ) | convert data to factor | factor(x,levels=...,labels=...) |
| merge( ) | join two data frames | see help file for details and examples |
| Basic Statistics | ||
| mean( ) | sample mean | see also: weighted.mean( ) |
| median( ) | sample median | |
| sd( ) | sample standard deviation | |
| var( ) | sample variance | |
| max( ) | maximum | |
| min( ) | minimum | |
| quantile( ) | sample quantiles | quantile(x,c(.1,.25,.5,.75,.9)) #a five-number summary of x |
| rank( ) | sample rank | |
| tabulate( ) | count entries | x =rep(1:5,c(2,2,4,3,6)) tabulate(x) |
| apply() | apply a function to a data frame | apply(X,1,sum): sum the rows of X apply(X,2,sum): sum the columns of X |
| Hypothesis Tests | ||
| binom.test( ) | exact test for binomial proportions | |
| prop.test( ) | large sample test for binomial proportions | |
| power.prop.test( ) | large sample binomial power computations | |
| t.test( ) | t test | t.test(x,mu=0): one sample t test t.test(x,y,var.equal=TRUE): two sample t test, equal variances t.test(x,y,paired=TRUE): paired sample t test |
| power.t.test( ) | t test power computations | |
| aov( ) | analysis of variance | aov(y ~ A, data=DF) |
| power.anova.test( ) | analysis of variance power computations | |
| wilcox.test( ) | Wilcoxon rank tests | non-parametric analogs of the t test |
| fisher.test( ) | Fisher's exact test | |
| ks.test( ) | Kolmogorov-Smirnov test | |
| shapiro.test( ) | Shapiro-Wilk test for normality | |
| Statistical Models | ||
| lm( ) | linear models (regression) | lm(y ~ x, data=DF) |
| nls( ) | non-linear least squares | |
| glm( ) | generalized linear model | |
| summary( ) | model summary | summary(lm(y ~ x, data=DF)) |
| Graphics | ||
| plot( ) | scatterplots | plot(x,y) or plot(y ~ x) |
| identify( ) | interactive identification of points | plot(x,y) identify(x,y) |
| abline( ) | add line to scatterplot | abline(a,b) add the line with intercept a and slope b |
| qqplot( ) | quantile-quantile plots | qqplot(x,y) |
| qqnorm( ) | normal quantile plots | qqnorm(x); qqline(x) |
| Input/Output | ||
| scan( ) | read a vector of data | scan("myfile"): read the data stored as plain text in "myfile" |
| read.table( ) | read plain text tabular data | read.table("myfile",header=TRUE) |
| write.table( ) | write a dataframe to a plain text file | you may need to set the working directory first |
| data.entry( ) | spreadsheet data entry | data.entry(x,y): datasets x and y must already exist |