[Gnuplot-info] log(xy) not turning out to be log(x) + log(y)

[Anirban G. <gan...@gm...>]

Hi,

I used the following simple gnuplot script written below :

 set terminal postscript enhanced color 'Helvetica' 20
 p(x,y,n1,n2) = log10((x**n1) * (abs(y)**n2)) + log10(x)
 q(x,y,n1,n2) = log10((x**n1) * x * (abs(y)**n2))
 set output 'plot499.ps'
 plot 'tsorted499diffVsB.dat' u (p(499,$1,3,0.66)):(p(499,$5,2,1)) every
::27::44 w p ls 1 t 'N=499(add)', 'tsorted499diffVsB.dat' u
(q(499,$1,3,0.66)):(q(499,$5,2,1)) every ::27::44 w p ls 2 t
'N=499(multiply)'
 set terminal x11

Note that the functions p and q are the same function using the idea that
log(product of two numbers) = sum of log of the two numbers, but the plot
command does not result in overlapping plots. I have attached the data
file  'tsorted499diffVsB.dat' and the output file 'plot499.ps' here. Any
help/clue as to what might be happening here will be appreciated.

Anirban