dateCols: Identify YMD names in a character vector

Description

grep for YMD (year, month, day) in col.names. Return a named list of integer vectors of length 3 for each triple found.

Usage

dateCols(col.names, YMD=c('Year', 'Month', 'Day'))

Arguments

col.names

either a character vector in which to search for names matching YMD or an object with non-null colnames

YMD

a character vector of patterns to use in grep to identify triples of columns coding YMD in col.names

Value

Returns a named list of integer vectors of length 3 identifying the positions in col.names of the desired date components.

Details

The data sets from the Correlates of War project include dates coded in triples of columns with names like c("StartMonth1", "StartDay1", "StartYear1", "EndMonth1", ..., "EndYear2"). This function will find all relevant date triples in a character vector of column names and return a list of integer vectors of length 3 with names like "Start1", "End1", ..., "End2" giving the positions in col.names of the desired date components.

Algorithm:

1. if(!is.null(colnames(YMD)))YMD <- colnames(YMD)

2. ymd <- grep for YMD (Year, Month, Day) in col.names.

3. groupNames <- sub pattern with '' in ymd

4. Throw a warning for any groupNames character string that does not appear with all three of Year, Month, and Day.

5. Return a list of integer vectors of length 3 for each triple found.

Examples

Run this code

# NOT RUN {
##
## 1.  character vector 
##
colNames <- c('war', 'StartMonth1', 'StartDay1', 'StartYear1', 
  'EndMonth1', 'EndMonth2', 'EndDay2', 'EndYear2', 'Initiator')

colNums <- dateCols(colNames)
# Should issue a warning:  
# Warning message:
# In dateCols(colNames) :
#   number of matches for Year = 2 != number of matches for Month = 3

# check 
colN <- list(Start1=c(Year=4, Month=2, Day=3), 
             End2=c(Year=8, Month=6, Day=7) )
# }
# NOT RUN {
all.equal(colNums, colN)
# }
# NOT RUN {
##
## 2.  array 
##
A <- matrix(ncol=length(colNames), 
      dimnames=list(NULL, colNames))

Anums <- dateCols(A)

# check 
# }
# NOT RUN {
all.equal(Anums, colN)
# }