Removing unwanted gridlines in RRDtool - rrdtool

Question

I'm currently making a number of graphs for users on a server.
The code 'm using is as follows:
$RRDTOOL graph $SCUMCOUNTPATH/mtghour.png \
--start now-3600s --end now \
--alt-autoscale \
-w 343 -h 85 \
--lower-limit 0 \
--title "Last 90 Minutes" \
--color CANVAS#36393f00 \
--color BACK#36393f00 \
--color FONT#5b80e0 \
--color GRID#888888 \
--color MGRID#888888 \
--color SHADEA#36393f \
--color SHADEB#36393f \
--x-grid MINUTE:5:HOUR:20:MINUTE:30:0:%M \
--alt-y-grid --rigid \
--left-axis-format %2.0lf \
--rigid \
--watermark "$(date +'%a %b %d %H:%M %Z %Y')" \
DEF:nowcount=$SCUMCOUNTPATH/mtg.rrd:count:AVERAGE \
CDEF:up=nowcount,0,*,0,EQ,0,1,IF \
TICK:up#3b455e:1.0 \
LINE2:nowcount#5b80e0: \
GPRINT:nowcount:LAST:" Current\:%2.0lf" \
GPRINT:nowcount:AVERAGE:"Average\:%2.1lf" \
GPRINT:nowcount:MAX:"Maximum\:%2.0lf " >/dev/null
What this produces is this:
What I would like it to produce is this (Photoshopped):
Extra info:
I'm using RRDtool 1.5.5 in a linux environment and running the script with BASH scheduled with cron.

Answer 1

The option you require is --y-grid, or possibly --alt-y-grid.
First try using --alt-y-grid which tries to use a more intelligent algorithm to calculate optimum line placement. It might work better for you in general.
Failing that, try --y-grid 1:1. This means "put a line every 1.0, and label every line". As comparison, what you're seeing in your first graph (that you don't want) is --y-grid 0.1:10 where a line goes every 0.1 but only 1 in 10 are labelled.
More details in the RRDTool documentation here