I want to scale my "y" data with some function in Gnuplot.

My data file "LB.dat"

 #x            #y
0.393000E+01 0.777894E+01
0.394000E+01 0.878703E+01
0.395000E+01 0.995059E+01
0.396000E+01 0.113780E+02
0.397000E+01 0.132372E+02
0.398000E+01 0.158209E+02
0.399000E+01 0.197064E+02
0.400000E+01 0.261749E+02
0.401000E+01 0.378215E+02
0.402000E+01 0.413921E+02
0.403000E+01 0.187385E+01
0.404000E+01 0.479743E+01
0.405000E+01 0.209362E+02
0.406000E+01 0.615307E+02
0.407000E+01 0.192419E+03
0.408000E+01 0.822545E+02
0.409000E+01 0.147813E+02
0.410000E+01 0.253664E+01
0.411000E+01 0.964172E-01
0.412000E+01 0.443564E+00

I want to scale my "y" data using the function exp(-a*"y") where 'a' is some constant.

Here is my script file.

set terminal postscript eps enhanced "Helvetica" 18 color
set output "scaling.eps"
set size 1,1
set xlabel "x" font "Helvetica,22"
set xrange[0:100]
set logscale y
set format y "10^{%L}"
set ylabel "y" font "Helvetica,22"

plot "LB.dat" using 1:exp(-0.5*$2) w l lw 1.5 lc 'blue' title "scaledLB"

When I run it I am getting an error message " plot "LB.dat" using 1:exp(-0.5*$2) w l lw 1.5 lc 'blue' title "scaledLB"

                               ^
     "scale.gp", line 13: undefined value "

Please help me resolve this issue.