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1) compatibility with S-Plus, which was widely used by statisticians for long before R 2) developing new statistical methods and other innovations (knitr, etc)
by grayclhn 12y ago
1) compatibility with S-Plus, which was widely used by statisticians for long before R
2) developing new statistical methods and other innovations (knitr, etc) is much easier in R or S-Plus than SAS, SPSS, etc. So R's improved a lot faster than the others.