internal error: stack not empty

[yi lu]

I tried to plot a graph that used mometum against its events.

The graph looks all right but when I tried to run it, it always show internal error: stack not empty. 

Here is my script:

reset;

set terminal x11;

set termopt enhanced;

set termopt font "Helvetica,24";

bin_width = 0.25;  # bin width in GeV

bin_number(x) = floor(x/bin_width);

binc(x) = bin_width * ( bin_number(x) + 0.5 );

total_protons = 12500.0;

isType(x,type) = (x==type)

piplus = 8; piminus=9; Kplus = 11; Kminus = 12; KOL= 10; KOS=16;

proton = 14; antiproton = 15; neutron = 13; lambda = 18;

mom(px,py,pz) = sqrt(px*px+py*py+pz*pz);

tan(px,py,pz)=(sqrt(px*px+py*py)/pz);

datafile =  "~/Desktop/120gev_hg_total_data.txt";

set xlabel "Angle";

set ylabel "Number of pions"; 

bin_width = 1;

plot datafile using (binc(tan($4,$5,$6))):(isType($7,piplus)/total_protons) \

title "{/Symbol p}^{+}" smooth frequency w points;

and attachment is part  of the data

since it is too big

Untitled 2.rtf
Description: RTF file