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--- notes:r_cheat_sheet [2026/07/30 08:13]
39.34.133.128 old revision restored (2014/10/01 03:37)
+++ notes:r_cheat_sheet [2026/07/31 21:41] (current)
163.227.87.117 old revision restored (2026/06/08 21:54)
@@ 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 =====
@@ Line 47: / Line 54: @@
 ===== Statistics =====
-  * ''mean(myvec)'' returns the mean.
+  * ''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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