Demonstrate Some Optimizations to Crayon Substring

optim.R

## Lightly edited for clarity

R version 3.2.2 (2015-08-14) -- "Fire Safety"

> install.packages("crayon")
trying URL 'http://cran.r-project.org/bin/macosx/mavericks/contrib/3.2/crayon_1.3.1.tgz'
Content type 'application/x-gzip' length 604079 bytes (589 KB)
==================================================
downloaded 589 KB

> x <- capture.output(matrix(runif(1000), ncol=10))
> library(microbenchmark)
> library(crayon)
> microbenchmark(substr(x, 1, 20), col_substr(x, 1, 20), times=10)
Unit: microseconds
                 expr        min         lq       mean     median         uq
     substr(x, 1, 20)     35.568     35.952     37.161     37.699     37.853
 col_substr(x, 1, 20) 121841.904 123384.504 128270.798 123884.187 128922.810
        max neval
     39.213    10
 159359.228    10
> remove.packages("crayon")
Removing package from ‘/Library/Frameworks/R.framework/Versions/3.2/Resources/library’
(as ‘lib’ is unspecified)
> q()
Save workspace image? [y/n/c]: y

[Previously saved workspace restored]

> devtools::install()
Installing crayon
* DONE (crayon)
> library(crayon)
> library(microbenchmark)
> microbenchmark(substr(x, 1, 20), col_substr(x, 1, 20), times=10)
Unit: microseconds
                 expr       min        lq       mean     median        uq
     substr(x, 1, 20)    35.412    35.787    41.5175    37.1525    39.909
 col_substr(x, 1, 20) 19951.044 21544.627 22157.1421 21905.3320 22659.350
       max neval
    78.953    10
 25438.851    10