[Gnuplot-info] Plot time series with different colored points

[<sfg...@gm...>]

Hi folks,

I want to plot time series data where the color of a point depends on
the hour the data is  measured (0 to 23 hour). But I can't figure out
how to do this. Here is my example:

reset
set xlabel "Date"
set xdata time
set timefmt '"%Y-%m-%d %H:%M"'
set format x "%m-%d"
set xtics nomirror
set ylabel "Y"
set palette model RGB defined ( 0 'green', 23 'blue' )
set cbrange [0:23]

T(N) = tm_hour(timecolumn(N,'"%Y-%m-%d %H:%M"'))

plot '-' u 1:2:T(1) with linespoints axis x1y1 title 'Y' ps 2 lw 2 palette
"2015-12-15 Tue 07:40" 2.4  
"2015-12-15 Tue 21:48" 1.7  
"2015-12-16 Wed 08:13" 2.5  
"2015-12-17 Thu 08:54" 2.6  
"2015-12-17 Thu 21:41" 2.2  
"2015-12-18 Fri 08:05" 2.1  
"2015-12-19 Sat 10:35" 3.6  
"2015-12-20 Sun 11:40" 3.6  
"2015-12-21 Mon 09:32" 4.5  
EOF
 
I got "unknown type in magnitude()" error. Any hints how to resolve
this? Thanks, Sven