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Function RKFERR
This function returns the absolute error estimate for a given step when solving
a problem as that described for function RKF. The input stack looks as
follows:
2: {‘x’, ‘y’, ‘f(x,y)’}
1:
∆
x
After running this function, the stack will show the lines:
4: {‘x’, ‘y’, ‘f(x,y)’}
3:
ε
2:
∆
y
1: error
Thus, this function is used to determine the increment in the solution,
∆
y, as
well as the absolute error (error).
The following screen shots show the RPN stack before and after application of
function RKFERR:
These result show that
∆
y = 0.827… and error = -1.89…
×
10
-6
.
Function RSBERR
This function performs similarly to RKERR but with the input elements listed for
function RRK. Thus, the input stack for this function will look as follows:
2: {‘x’, ‘y’, ‘f(x,y)’ ‘
∂
f/
∂
x’ ‘
∂
f/vy’ }
1:
∆
x
After running the function, the stack will show the lines:
4: {‘x’, ‘y’, ‘f(x,y)’ ‘
∂
f/
∂
x’ ‘
∂
f/vy’ }:
3:
ε
2:
∆
y
1: error
