size/origin & {r,l,t,b}margin

[Ben Abbott]

If I understand this correctly, the commands below will produce a plot
whose plot box (axes), tick-labels, axes-labels, and title will be inside
the rectangle defined by the "size" and "origin".

        set size <width>,<height>
        set origin <xLL>,<yLL>
        set xlabel "my xlabel"
        set ylabel "my ylabel"
        set title "my title"
        plot sin(x)

While the commands below will produce a result where the plot box
(axes) are defined to be bounded the specified left, right, top, and
bottom margins.

        set lmargin at screen <xLeft>
        set rmargin at screen <xRight>
        set tmargin at screen <yTop>
        set bmargin at screen <yBottom>
        set xlabel "my xlabel"
        set ylabel "my ylabel"
        set title "my title"
        plot sin(x)

When specifying "size" and "origin" is there a way to determine the
resulting plot box locations, the equivalent {r,l,t,b}margins?

Also, when specifying {r,l,t,b}margins (with the "at screen" qualifier)
is there a way to determine the effective "size" and "origin"?

Ben