R Language: A Quick Reference – III

R Programming: A Quick Reference

R language: A Quick Reference is about learning R Programming with a short description of the widely used commands. It will help the learner and intermediate user of the R Programming Language to get help with different functions quickly. This Quick Reference is classified into different groups. Let us start with R Language: A Quick Reference – III.

This R Language: A Quick Reference contains R commands about subsetting of vectors, matrices, lists, data frames, arrays, and factors. It also discusses setting the different properties related to R language data types.

Subsetting Vectors in R Language

The following are ways to subset or slice the values from a vector.

R CommandShort Description
x[1:5]Select elements of $x$ by index
x[-(1:5)]Exclude elements of $x$ by index
x[c(TRUE, FALSE)]Select elements of $x$ corresponding to the True value
x[c(“a”, “b”)]Select elements of $x$ by name

Subsetting Lists in R Language

The following methods are used to subset of slice a list in R Language.

R CommandShort Description
x[1:5]Extracts a sublist of the list $x$
x[-(1:5)]Extract a sublist by excluding elements of list $x$
x[c(TRUE, FALSE)]Extract a sublist with logical subscripts
x[c(“a”, “b”)]Extract a sublist by name
x[[2]]Extract an element of the list $x$
x[[“a”]]Extract the element with the name “a” from list $x$
x$aExtract the element with the name “a” from list $x$

Subsetting Matrices in R Language

To subset or extract certain elements from a matrix follow the ways described below.

R CommandShort Description
x[i, j]Extracts elements of matrix $x$, specified by row $i$ and column $j$
x[i, j] = vSet or rest the elements of matrix $x$, specified by row $i$ and column $j$
x[i, ]Extracts $i$th row of a matrix $x$
x[i, ] = vSet or resets the $i$th row of a matrix $x$ specified by $i$th row
x[ , j]Extracts the $j$ column of a matrix $x$
x[ , j] = vSets or resets the $j$ column of matrix $x$
x[i]Subets a matrix $x$ as a vector
x[i] = vSets or resets the $i$th elements (treated as a vector operation)

Subsetting a Data Frame in R Language

One can easily subset or slice a Data Frame in R.

R CommandShort Description
df[i, j]Matrix subsetting of a data frame, specified by $i$th row and $j$th column
df[i, j] = dfvSets or resets a subset of a data frame
subset(df, subset = i)Subset of the $i$ cases/ observations of a data frame
subset(df, select = i)Subset of the $i$ variables/ columns of a data frame
subset(df, subset=i, select=j)Subset of the $i$ cases and $j$ variables of a data frame

R Language: A Quick Reference – I

R Language: A Quick Reference – III

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