Drawing box plot with gnuplot 4.6

Question

In the official document in page 44 it says, to draw a boxplot

# Place a boxplot at x coordinate 1.0 representing the y values in column 5
plot 'data' using (1.0):5

I cannot get it work, when I do above gnuplot only draws points, not a box. Anybody knows how to do it? In the guide, the example shows a box plot (page 44 the figure on the right)

I am using gnuplot 4.6 patch level 4. I am not getting any errors, but the box is just not there.

When I use the demo script

plot 'silver.dat' using (1):2, '' using (2):(5*$3)

it works, what does the second part after the comma mean? ( '' using (2):(5*$3) )

Answer 1

I was specifying box widths, but finally found that this should be added at least

set style data boxplot

optionally, you can add

set style fill solid 0.25 border -1
set style boxplot outliers pointtype 7