R/MEDIPS.rms.R

In HPCBio/MEDIPS-BioC: DNA IP-seq data analysis

##########################################################################
##Function processes a MEDIPSset and weights the counts by the estimated coupling factor dependent signal of the calibration curve.
##Normalized counts are transformed into a rpkm scale.
##########################################################################
##Input:	MEDIPS SET, CS
##Output:	rms vector
##Modified:	1/9/2015
##Author:	Lukas Chavez

MEDIPS.rms <- function(MSet=NULL, CSet=NULL, ccObj=NULL){
	
	signal = genome_count(MSet)
	coupling = genome_CF(CSet)
		
	if(is.null(ccObj)){
		##Calculate calibration curve
		#####################################
		ccObj = MEDIPS.calibrationCurve(MSet=MSet, CSet=CSet, input=F)
	}

	##Weight signals by linear regression obtained parameters
	####################
	cat("Calculating relative methylation score...\n")
	
        estim=numeric(length(ccObj$mean_signal))

	##For the low range of the calibration curve (< max_index) divide counts by observed mean count
	low_range=1:ccObj$max_index
        estim[low_range]=ccObj$mean_signal[low_range]

	##For the higher range of the calibration curve (>=max_index) divide counts by estimated count
	high_range=(ccObj$max_index+1):length(estim)

	estim[high_range]=ccObj$intercept + (ccObj$slope * ccObj$coupling_level[high_range]) 

	#rms normalization:
	signal=signal/estim[coupling+1]
	signal[coupling==0]=0

	##Transform weighted signals into reads per thousand million
	if(class(MSet)=="MEDIPSset"){
		signal = (signal*10^9)/(window_size(MSet)*number_regions(MSet))
	}
	else{
		signal = (signal*10^9)/(as.numeric(width(rois(MSet)))*number_regions(MSet))
	}

	#Transform the resulting data range into the consistent interval [0:1] by trimming the upper 0.1 quantile of the data
	#######################
	signal = log2(signal)

	signal[is.na(signal)] = 0
				
	##Shift signals into positive value range
	####################
	minsignal=min(signal[signal!=-Inf])
	signal[signal!=-Inf]=signal[signal!=-Inf]+abs(minsignal)
	
	##Transform values into the interval [0:1] by compressing the top 20% of the signals
	####################
	maxsignal = max(signal[signal!=Inf])*0.8
	signal[signal!=Inf & signal>maxsignal]=maxsignal
	signal=round((signal/maxsignal), digits=2)

	##Eliminate -Inf & Inf --> 0
	#######################
	signal[signal==-Inf | signal ==Inf]=0

	return(signal)
}