[pstricks] logarithmic scale

[jmpapy]

Danke sehr Herbert! Postcript language is still unclear to me but I'm 
progressively learning.

I assume that :

\makeatletter
\pst at def{ScalePoints}<%
    /y ED /x ED % save the units
    counttomark dup dup cvi eq not { exch pop } if
    /m exch def /n m 2 div cvi def
    n {
       log y mul m 1 roll % <-- log of y-value
       x mul m 1 roll
       /m m 2 sub
       def } repeat>
\makeatother

is always in the document preamble. I should I proceed when I have 
several plots with a different scale in a document.

thank you again

JM