HP 50g Graphing manual Rkfstep, Problem for a differential equation, Is the rightshift 3key

•error displays the absolute error for that step. A zero error indicates that the Runge–Kutta– Fehlberg method failed and that Euler’s method was used instead.

The absolute error is the absolute value of the estimated error for a scalar problem, and the row (infinity) norm of the estimated error vector for a vector problem. (The latter is a bound on the maximum error of any component of the solution.)

Access:	…µRKFE
Input/Output:
		L2/A1	L1/A2		L4/I1	L3/I2	L2/I3	L1/I4
		{ list }	h	→	{ list }	h	ydelta	error
			L = Level; A = Argument; I = item
See also:	RKF, RKFSTEP, RRK, RRKSTEP, RSBERR
RKFSTEP	Command
Type:
Description:	Next Solution Step for RKF Command: Computes the next solution step (hnext) to an initial value
	problem for a differential equation.

The arguments and results are as follows:

•{ list } contains three items in this order: the independent (t) and solution (y) variables, and the righthand side of the differential equation (or a variable where the expression is stored).

•xtol sets the tolerance value.

•h specifies the initial candidate step.

•hnext is the next candidate step.

The independent and solution variables must have values stored in them. RKFSTEP steps these variables to the next point upon completion.

Note that the actual step used by RKFSTEP will be less than the input value h if the global error tolerance is not satisfied by that value. If a stringent global error tolerance forces RKFSTEP to reduce its stepsize to the point that the Runge–Kutta–Fehlberg methods fails, then RKFSTEP will use the Euler method to compute the next solution step and will consider the error tolerance satisfied. The RungeKuttaFehlberg method will fai l if the current independent variable is zero and the stepsize ≤ 1.3 × 10498 or if the variable is nonzero and the stepsize is 1.3 × 1010 times its magnitude.

Access:	…µRKFS
Input/Output:
		L3/A1	L2/An	L1/An+1		L3/I1	L2/I2	L1/I3
		{ list }	xtol	h	→	{ list }	xtol	hnext
			L = Level; A = Argument; I = item
See also:	RKF, RKFERR, RRK, RRKSTEP, RSBERR
RL	Command
Type:
Description:	Rotate Left Command: Rotates a binary integer one bit to the left.
	The leftmost bit of #n1 becomes the rightmost bit of #n2.
Access:	…ÃBIT RL			(Ã is the rightshift of the			3key).
Flags:	Binary Integer Wordsize (–5 through –10), Binary Integer Base (–11, –12)

3204 Full Command and Function Reference