My code below, example, to have the layout three graph in a the same row and in png format I should add after end gpbuild:
set verbose off
strings CoalW
gpbuild CoalW
gnuplot 2 --with-lines --time-series { set grid; set title "Gráfico A. Precio del Carbón en Londres"; set ylabel "Peniques por tonelada"; set xtics 1700, 25; }
gnuplot 7 --with-lines --time-series { set grid; set title "Gráfico B.Salario real"; set ylabel "salario en gramos de plata"; set xtics 1700, 25;}
gnuplot 9 --with-lines --time-series { set grid; set title "Gráfico C.Producto Industrial"; set ylabel "Índice"; set xtics 1700, 25; }
end gpbuild
gridplot CoalW --output=display