# example - gawk -f columnStDev.awk Columns="-3-" data/subsets/coc81_all.csv.converted
# or		gawk -f columnStDev.awk I=3 data/subsets/coc81_all.csv.converted

BEGIN {
	FS=OFS=","
	Sum=0;
	SumSq=0;
	I=1;
	Columns="";
}

NR==1 {
	for(x=1; x<=NF; x++) {
		target="-"x"-";
		if (index(Columns, target)!=0) { I=x; }
	}	
}

{
	Sum	+= $I
	SumSq += $I^2  
}
	
END {
	result = sd(SumSq,Sum,NR);
	print result;
}

function sd(sumSq,sumX,n) {
	val=(sumSq-((sumX*sumX) / n)) / (n-1)
	magval= val < 0 ? -1* val : val;
	return sqrt(magval)
	#return sqrt((sumSq-((sumX*sumX) / n)) / (n-1))
}