import rrdtool
temps = rrdtool.fetch("-s -24h","temperature.rrd","AVERAGE")
mintemp = min(i[0] for i in temps[2] if i[0] is not None)
maxtemp = max(i[0] for i in temps[2] if i[0] is not None)
setup a rrd without data names, the default becomes 'value'
VDEF can't be output with XPORT
rrdtool graph \
"$1" \
--start end-$4 \
--width 1200 \
--height 600 \
--step "$5" \
--title "$3 sensors- $4" \
--vertical-label "degrees C / Humidity %/2 " \
--alt-autoscale \
--right-axis-label "Pressure hPa" \
--right-axis 1:988 \
--left-axis-format %.1lf \
--right-axis-format %.0lf \
--color "BACK#303030" \
--color "FONT#CCCCCC" \
--color "CANVAS#111111" \
"TEXTALIGN:left" \
"DEF:temperature=$2/temperature.rrd:value:AVERAGE" \
"DEF:humidity=$2/humidity.rrd:value:AVERAGE" \
"DEF:pressure=$2/pressure.rrd:value:AVERAGE" \
"DEF:dewpoint=$2/dewpoint.rrd:value:AVERAGE" \
"AREA:temperature#00bc8c:temperature C" \
"AREA:dewpoint#3498db:dewpoint C" \
"CDEF:presplot=pressure,988,-"\
"CDEF:halfhumid=humidity,.5,*"\
"LINE2:presplot#e74c3c:Pressure hPa" \
"LINE2:halfhumid#f39c12:Humidity %/2" \
"VDEF:pmax=pressure,MAXIMUM" \
"VDEF:pavg=pressure,AVERAGE" \
"VDEF:pmin=pressure,MINIMUM" \
"VDEF:ppmax=presplot,MAXIMUM" \
"VDEF:ppavg=presplot,AVERAGE" \
"VDEF:ppmin=presplot,MINIMUM" \
"LINE1:ppmax#e74c3c:max pressure\\::dashes" \
"GPRINT:pressure:MAX:%4.1lf" \
"LINE1:ppmin#6610f2:min pressure\\::dashes" \
"GPRINT:pressure:MIN:%4.1lf" \
"VDEF:hmax=halfhumid,MAXIMUM" \
"VDEF:havg=halfhumid,AVERAGE" \
"VDEF:hmin=halfhumid,MINIMUM" \
"LINE1:hmax#e74c3c:max humidity\\::dashes" \
"GPRINT:humidity:MAX:%4.1lf" \
"LINE1:hmin#6610f2:min humidity\\::dashes" \
"GPRINT:humidity:MIN:%4.1lf" \
"VDEF:tmax=temperature,MAXIMUM" \
"VDEF:tavg=temperature,AVERAGE" \
"VDEF:tmin=temperature,MINIMUM" \
"LINE2:tmax#e74c3c:max temp\\::dashes" \
"GPRINT:temperature:MAX:%4.1lf" \
"LINE2:tmin#6610f2:min temp\\::dashes" \
"GPRINT:temperature:MIN:%4.1lf" \
--watermark "Drawn: $nowlit";
}