Note that this tutorial only applies to the old style
editor. This one is still available in TouchPlot 4 provided
you edit Touchplot’s application preference (Settings
application). For the new editor, have a look at the movies
for version 4.0, or at the embedded documentation.

Designing a formula editor is not an easy task, and the
absence of a physical keyboard on the iPhone or iPod touch
doesn't make it any easier. I decided to use direct polish
notation to enter a formula. It has the benefit of not
needing to enter any parenthesis and minimizing the number
of touches... It has a drawback though, one needs some time
to get used to it !

Rather than describe it in theory, lets just study some
examples : to enter a formula using direct polish notation,
you have some work to do : you have to analyse the formula
and be able to tell : this is a sum, this is a product,
this is the sinus of something... Then you have it : if it
is a sum, you hit +, then you compose the left part of the
sum, then the right part.

Note that since version 2.2, and even more with 3.2
version, things have become much easier for those having
difficulties with polish notation. One could even enter a
formula never using polish notation, but the most
convenient and fast way still remains using direct polish
notation.