def lpf(infile, outfile, columns, dt, rc)
	h = File.open(outfile, 'w')
	prop = dt.to_f / (rc + dt).to_f
	puts prop
	last_values = [0.0] * columns.length
#	counter = 0
	IO.foreach(infile) { |row|
#		break if counter == 100
#		counter += 1
		data = row.split(',')
		new_columns = []
		columns.length.times { |i|
			c_id = columns[i]
			value = prop * data[c_id].to_f + (1 - prop) * last_values[i]
			new_columns << value
			last_values[i] = value
		}
		h.write "#{row.strip},#{new_columns.join(',')}\n"
#		puts "#{row.strip.gsub ',', "\t"}\t#{new_columns.join("\t")}\n"
	}
end