update centile_band_for_centile, now calculates the ranges for within centile band by using sds_of_centile_line +/- (1/4 * 0.666).
centile spaces are all the same size, 0.666SD
centile_band_for_centile function takes a new parameter of centile_format so it knows whether to use the 6-centile or the 9-centile pattern
update centile_band_for_centile, now calculates the ranges for within centile band by using sds_of_centile_line +/- (1/4 * 0.666). centile spaces are all the same size, 0.666SD
centile_band_for_centile function takes a new parameter of centile_format so it knows whether to use the 6-centile or the 9-centile pattern