\CANCEL MODE VERIFY
! overlay_bars.jnl 10/96

! DESCRIPTION: Overlay error bars on a time series (or frequency) plot

! This is a simple routine to overlay error bars. It is applicable only to
! T axis plots and it creates only a simple vertical line (no I bar).

! A more sophisticated script could be both faster and higher functioning.

! Usage:                   1        2      3
!       GO overlay_bars spectrum errors [color]

! Arguments:

!  spectrum - 1D field to be plotted (on T axis)
!
!  errors   - a 1D field of errors (bars from spectrum-error to spectrum+error)
!
!  color    - color of the error bars

! check color parameter
DEFINE SYMBOL ob_color $3"1|1|2|3|4|5|6|7|8|9|10|11|12|13|14|black>1|red>2|green>3|blue>4|<Unknown color argument"

! define a 2-point vertical line with this variable
LET/QUIET kk=k		! to work around a known bug in Ferret V4.4
LET/QUIET vbar = if kk eq 1 then (-1)*$2 else $2

! error bar plot
REPEAT/L=`$1,return=lstart`:`$1,return=lend` PLOT/OVER/VS/LINE=($ob_color)/K=1:2/NOLAB $1*kk*0+T,$1+vbar

! clean up
CANCEL REGION/l
CANCEL VARIABLE kk, vbar
CANCEL SYMBOL ob_color
SET MODE/LAST VERIFY