icd9ComorbidMatToDf: convert matrix of comorbidities into data frame, preserving...
In jackwasey/icd9: Tools for Working with ICD-9 Codes, and Finding Comorbidities

convert matrix of comorbidities into data frame, preserving visitId information

1 2	icd9ComorbidMatToDf(x, visitId = "visitId", stringsAsFactors = getOption("stringsAsFactors"))

`x`	Matrix of comorbidities, with row and columns names defined
`visitId`	Single character string with name for new column in output data frame. Everywhere else, `visitId` describes the input data, but here it is for output data.
`stringsAsFactors`	whether the resulting data frame should have strings, i.e. visitId converted to factor. Default is to follow the current session option.

longdf <- data.frame(visitId = c("a", "b", "b", "c"),
    icd9 = c("441", "4424", "443", "441"))
mat <- icd9ComorbidElix(longdf)
class(mat)
typeof(mat)
rownames(mat)
df.out <- icd9ComorbidMatToDf(mat)
stopifnot(is.data.frame(df.out))
# output data frame has a factor for the visitId column
stopifnot(identical(rownames(mat), as.character(df.out$visitId)))
df.out[, 1:4]