# Solution to I590/N560 R assignment #2, due 13 Oct. 2006 - Don Byrd

# setwd("Documents/Music+AudioIR+DLs/RProgramming")  # OS X (Don's G4; use YOUR path!)
setwd("Desktop/TODAY")  # OS X (M373 Mac)
# setwd("C:/Documents and Settings/donbyrd.ADS/Music+AudioIR/Teaching+ClassGuestLectures/INFON560-Fall2006/IntervalFreqRAssignment")
    # Windows (Don's PC)

# Read in the file and grab the number of notes it contains.
noteTable = read.table("Dichterliebe01PMIDI.txt", header=TRUE)
noteCount = length(noteTable$DataByte)

# Create array of length to hold count for each interval, and initialize all the
#   elements to zero.
intervalCount = seq(from=0, to=0, length.out=12)

# For each note after the first, compute the interval from the previous note; then
#   compute the pitch class (0 to 11) of its abs. value, and add one to the count for
#   that pitch class. Unfortunately, arrays in R start with index 1 instead of 0, so
#   we have to add 1 to all the indices.
for (i in 1:noteCount-1) {
    diff = noteTable$DataByte[i+1]-noteTable$DataByte[i]
    diffPC = abs(diff) %% 12
    intervalCount[diffPC+1] = intervalCount[diffPC+1]+1 
}

# Finally, display the interval counts (a) numerically, and (b) in a histogram
#   labelled with the correct intervals (0 to 11, not 1 to 12).
intervalCount
interval = seq(from=0, to=11, length.out=12)
plot(interval, intervalCount, type="h", xlab="interval (half-steps)")