change font size on gnuplot

Question

I know there have been several posts on how to change the font size on gnuplot. However, in my code, even though I take the solution in previous posts, the output figures have no change. My code is :

set terminal png size 1280, 480;
set xrange [0:100]
set yrange [0:1]
set xlabel 'n'
set ylabel 'x_n'
set tics font ",1"
set output './time_series/r'.i.'.'.j.''.k.''.l.'.png';
set title 'r = '.i.'.'.j.''.k.''.l;

do for [i=0:3]{
    do for [j=0:9]{
    do for [k=0:9]{
    do for [l=0:9]{
    plot './time_series/r'.i.'.'.j.''.k.''.l.'.txt' every ::0::100 with linespoints ls 1 ps 1 pt 7 notitle
    }
    }
    }
}

The command has no effect with any number I put into, i.e.

set tics font ",a number"

Any number produces the same font. Is there anything I missed?

Thank you everyone.

Update : Thanks Raphael. Here are two png produced. The first is with [set tics font ",1"]. The second, [set tics font ",10"].

Answer 1

AD1: the correct way to set tics font size is

set tics font "name{,<size>}"

eg.

set tics font "Helvetica,10"

AD2: set tics font resizes only the fonts of x-y axes. To resize all the fonts (eg. the title) use

set terminal png size 1280, 480 font "Helvetica,30"

(or any other fontname and/or size :o) )