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--- notes:r_cheat_sheet [2026/11/02 15:32]
47.79.201.228 old revision restored (2026/06/22 06:56)
+++ notes:r_cheat_sheet [2026/11/04 09:00] (current)
95.87.69.121 old revision restored (2026/09/04 13:03)
@@ Line 20: / Line 20: @@
   * ''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)]''
-  * 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')
 myseq['two']</code>
@@ Line 26: / Line 26: @@
   * Scalar operations or functions on vectors typically produce other vectors e.g. + - == sin(myseq)
+===== 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''
 ===== 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>
 x=seq[0,20,.1]
@@ Line 45: / Line 52: @@
   * ''mymatrix[,2]'' returns entire second column.
+===== Statistics =====
+  * ''mean(myvec)  median(myvec)   sd(myvec)''
 ===== File Handling =====
   * ''list.files()'' to list files in furrent directory
   * ''source("file.R")'' to load file of code
+  * ''read.csv('mydat.csv')'' to load a csv file

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