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notes:r_cheat_sheet

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notes:r_cheat_sheet [2026/06/10 20:38]
43.133.3.6 old revision restored (2026/05/30 10:47) 		notes:r_cheat_sheet [2026/06/13 20:30] (current)
216.73.217.75 old revision restored (2026/06/12 20:50)
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   * ''R'' is the command-line interpreter   * ''R'' is the command-line interpreter
 +  * ''install.pa­ckages("gg­plot2") '' to install additional packages
 +
   * Expressions are evaluated and displayed e.g. 1, 1+1, "Hello World"   * Expressions are evaluated and displayed e.g. 1, 1+1, "Hello World"
   * Booleans are e.g. ''1=1'' , ''3>4'' , ''TRUE'', T, ''FALSE'', F   * Booleans are e.g. ''1=1'' , ''3>4'' , ''TRUE'', T, ''FALSE'', F
   * For variable assignment ''x=1'' or ''x<-1''   * For variable assignment ''x=1'' or ''x<-1''
-  * For help on a function use ''help(sum)'' or ''example(sqrt)''+  * For help on a function use ''help(sum)'' ,  ''help(package='ggplot2')''  or ''example(sqrt)''
   * Operations are ''+ - * / = <-''   * Operations are ''+ - * / = <-''
   * ''NA'' is used to express a missing or unknown data  value. Expressions on NA return NA.   * ''NA'' is used to express a missing or unknown data  value. Expressions on NA return NA.
- 
 ===== Vectors ===== ===== Vectors =====
   * To create a vector, use the combine command ''c(4,7,9)''   * To create a vector, use the combine command ''c(4,7,9)''
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   * ''myseq[3]'' to access third element i.e. vectors indexed starting at 1.   * ''myseq[3]'' to access third element i.e. vectors indexed starting at 1.
   * Use a vector as an index to access multiple elements e.g. ''myseq[c(1,3)]''   * Use a vector as an index to access multiple elements e.g. ''myseq[c(1,3)]''
-  * The ''names'' function can be used to assign names to vector elements. Once names are asigned, they can be sed as indices e.g. <code>+  * The ''names'' function can be used to assign names to vector elements. Once names are asigned, they can be used as indices e.g. <code>
 names(myseq)=c('one','two','three') names(myseq)=c('one','two','three')
 myseq['two']</code> myseq['two']</code>
   * ''myseq + 1'' adds one to all elements of the myseq vector.   * ''myseq + 1'' adds one to all elements of the myseq vector.
   * Scalar operations or functions on vectors typically produce other vectors e.g. + - == sin(myseq)   * Scalar operations or functions on vectors typically produce other vectors e.g. + - == sin(myseq)
 +  * ''head(myvec)'' , ''tail(myvec)'' to show start or end of vector
  
 ===== Plotting ===== ===== Plotting =====
  
-  * ''barplot[myseq]'' creates a bar plot of the ''myseq'' vector.+  * ''barplot[myseq]'' creates a bar plot of the ''myseq'' vector. ''abline(h=y)'' plots a horizontal line at height y.
   * ''plot[x,y]'' plots x vs y e.g. <code>   * ''plot[x,y]'' plots x vs y e.g. <code>
 x=seq[0,20,.1] x=seq[0,20,.1]
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   * ''persp(mymat)'' plots a contour map in perspective.   * ''persp(mymat)'' plots a contour map in perspective.
   * ''image(volcano)'' generates a heat map of the matrix.   * ''image(volcano)'' generates a heat map of the matrix.
 +  * ''qplot(weights, prices, color=types)'' - more attractive plotting using ggplot2 package.
 ===== Matrices ===== ===== Matrices =====
  
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   * ''mymatrix[,2]'' returns entire second column.   * ''mymatrix[,2]'' returns entire second column.
  
 +===== Data Sets =====
 +  * ''factor'' is a collection type for categorized values - ''myfac=factor(myvec)''
 +  * ''factor''s group unique string values as ''level''s e.g. levels(myfac) shows unique levels. 
 +  * ''as.integer(myfac)'' shows levels as integers, can be used to set plot type
 +  * ''legend("to­pright", level­s(types), pch=1­:length(le­vels(types­)))''
 +  * A data frame collects sets of related values (i.e. sets of columns with values in the same order) e.g. ''mydf=data.frame(weights,prices,types)''
 +  * To extract a column, use double-square brackets with the column index or name e.g. ''mydf%%[['weights']]%%'' or just a dollar sign e.g. ''treasure$prices''
 +  * ''merge'' merges data sets by joining on shared column names
 +
 +===== Statistics =====
 +
 +  * ''mean(myvec)  median(myvec)   sd(myvec)''
 +  * ''cor.test'' tests for correlation (Pearson's product-moment)
 +  * ''line = lm(cola ~ colb)'' calculates a linear model between cola and colb that can be plotted with ''abline(line)''
 +  * 
 ===== File Handling ===== ===== File Handling =====
  
   * ''list.files()'' to list files in furrent directory   * ''list.files()'' to list files in furrent directory
   * ''source("file.R")'' to load file of code   * ''source("file.R")'' to load file of code
 +  * ''read.csv('mydat.csv')'' to load a csv file
 +  * ''read.table'' to read text data with other separators
 +  * ''con<-url("http://google.com","r")'' to read a webpage
 +  * ''x<-readLines(con)'' to convert to an array of lines
notes/r_cheat_sheet.1781149080.txt.gz · Last modified: 2026/06/10 20:38 by 43.133.3.6

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