min=-30
max=5
n=10
width=(max-min)/n #interval width
#function used to map a value to the intervals
hist(x,width)=width*floor(x/width)+width/2.0
set xrange [min:max]
#to put an empty boundary around the
#data inside an autoscaled graph.
#set offset graph 0.05,0.05,0.05,0.0
set xtics min,(max-min)/10,max
set boxwidth width*0.9
set style fill solid 0.5 #fillstyle
set tics out nomirror
plot 'dphi.dat' u (hist(($1),width)):(1.0) smooth freq w boxes lc rgb"green" not