Convert row data to binary columns

Question

I am attempting to format a column of data into many binary columns to eventually use for association rule mining. I have had some success using a for loop and a simple trip

Answer 1

This should do the trick:

## Get a contingency table of counts
X <- with(data, table(a,b))

## Massage it into the format you're wanting 
cbind(name = rownames(X), apply(X, 2, as.character))
#      name     brown green purple yellow
# [1,] "andy"   "0"   "1"   "0"    "0"   
# [2,] "george" "0"   "0"   "1"    "1"   
# [3,] "sally"  "1"   "1"   "0"    "0"   
# [4,] "sue"    "0"   "0"   "1"    "1"