RPL program for HP Calculator

[Lexus17]

Dear All,

I’ve been given a program in my HP50g calculator and I’m not familiar with the RPL language. However, I do need to understand
the program I’ve been given (I found a user’s guide on the net but the code I’ve been given looks sometimes different as what II can find in the user’s guide, which makes me lost), hence my request in getting some help from you please on a couple of (easy) lines, mainly referring to loops (FOR) and conditions (IFTE). I’ve extracted the part where I face difficulties and I’m putting my questions in italic. The context is a (symmetric) matrix called “ZE” whose I need to calculate each cell using parameters “PTCH”, “NS” and “RHC”, which are all three known numbers. Function ASINH refers to arc sinus hyperbolic.

FOR i i NS 1. +
From what value up to (NS+1) ”i” is supposed to go to ?
FOR j i 1. == 0.
What does this mean ? I’m lost in the conditions raised for i and j…

\<< PTCH i 1.5 - *
If my above condition is true, then my parameter PTCH is multiplied by (i-1.5), correct ?
\>> IFTE PTCH i NS 1. + ==
If i= (NS+1), then PTCH is to be multiplied by NS, correct ?
\<< NS *
\>>
\<< i .5 - *
Otherwise (above condition is false), PTCH is to be multiplied by (i-0.5), correct ?
\>> IFTE j 1. == 0.
If j is different from 1, correct ?
\<< PTCH j 1.5 - *
Then PTCH is to be multiplied by (j-1.5), correct ?
\>> IFTE PTCH j NS 1. + ==
\<< NS *
If j=NS+1, then PTCH needs to be multiplied by NS, correct ?
\>>
\<< j .5 - *
Otherwise, PTCH is multiplied by (j-1.5), correct ?

For the above, my issue is also to understand how conditions are inserted within each other…

\>> IFTE \-> z1 z2 z3 z4
I’m lost here… How are variables z1 to z4 calculated ?

\<< z3 z4 'ASINH((z2-z)/RHC)-ASINH((z1-z)/RHC)' 'z' \.S RHO * 2. / \pi \->NUM / z2 z1 - / z4 z3 - / DUP 'ZE' { i j } ROT PUT 'ZE' { j i } ROT PUT
\>>
What is the formulae here? In other words :
- How is “z” determined/calculated ?
- How variables z1 to z4 act in this above formulae ? Can somebody write it differently, e.g. in an Excel sheet ?
NEXT
NEXT ZE INV 'YE' STO
Matrix ZE is to be inversed
\>>