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--- notes:r_cheat_sheet [2026/11/03 07:05]
177.10.175.112 old revision restored (2026/08/03 07:09)
+++ notes:r_cheat_sheet [2026/11/03 12:36] (current)
216.73.216.223 old revision restored (2026/11/02 13:08)
@@ Line 44: / Line 44: @@
   * ''mymatrix[3,4]'' returns an element of the matrix (row,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)'' 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
+  * ''read.table'' to read text data with other separators

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