'Record' row values every time the binary value in a collumn changes

Hi:

Here are a couple more options using packages plyr and data.table. The
labels in the second part are changed because they didn't make sense
in a 2M line file (well, mine may not either, but it's a start). You
can always change them to something more pertinent.

# Question 1:
Table <- data.frame(binary, chromosome = Chromosome, start)

library(plyr)
(df <- ddply(Table, .(chromosome, binary), summarise, position_start =
min(start),
         position_end = max(start)))
  chromosome binary position_start position_end
1          1      0             20           36
2          1      1             12           18
3          2      0             17           19
4          2      1             12           16

library(data.table)
dTable <- data.table(Table, key = 'chromosome, binary')
(dt <- dTable[, list(position_start = min(start),
               position_end = max(start)), by = 'chromosome, binary'])
     chromosome binary position_start position_end
[1,]          1      0             20           36
[2,]          1      1             12           18
[3,]          2      0             17           19
[4,]          2      1             12           16

## Question 2:

For plyr, it's easy to write a function that takes a generic input data frame
(in this case, a single line) and then outputs a data frame with
positions and labels.

tfun <- function(df) {
     diff <- with(df, position_end - position_start + 1)
     position <- with(df, seq(position_start, position_end))
     value <- paste(df$chromosome, df$binary, letters[1:diff], sep = '.')
     data.frame(chromosome = df$chromosome, position, value, binary = df$binary)
    }

# Then:

'Record' row values every time the binary value in a collumn changes

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