HP 50g User's Reference Manual
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Brand: HP
Category: Calculator
Type: Advanced user's reference manual
Model: HP 48gII , HP 49g+ , HP 50G
Pages: 693
3-60 Full Command and Function Reference
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If axes contains any strings other than 0, 1 or n, the DIFFEQ plotter uses the default strings 0
and 1, and plots the independent variable on the horizontal axis and the dependent variable
on the vertical.
• ptype is a command name specifying the plot type. Executing the command DIFFEQ places the
command name DIFFEQ in PPAR.
• depend is a list, { Y y
0
x
ErrTol
}, containing a name that specifies the dependent variable (the
solution), and two numbers that specify the initial value of Y and the global absolute error
tolerance in the solution Y. The default values for these elements are { Y 0 .0001 }
EQ must define the right-hand side of the initial value problem Y'(XF(X,Y). Y can return a real
value or real vector when evaluated.
The DIFFEQ-plotter attempts to make the interval between values of the independent variable as
large as possible, while keeping the computed solution within the specified error tolerance x
ErrTol
.
This tolerance may hold only at the computed points. Straight lines are drawn between computed
step endpoints, and these lines may not accurately represent the actual shape of the solution. res
limits the maximum interval size to provide higher plot resolution.
On exit from DIFFEQ plot, the first elements of indep and depnd (identifiers) contain the final
values of X and Y, respectively.
If EQ contains a list, the initial value problem is solved and plotted using a combination of
Rosenbrock (3,4) and Runge-Kutta-Fehlberg (4,5) methods. In this case DIFFEQ uses
RRKSTEP to calculate y
f
, and EQ must contain two additional elements:
• The second element of EQ must evaluate to the partial derivative of Y' with respect to X, and
can return a real value or real vector when evaluated.
• The third element of EQ must evaluate to the partial derivative of Y' with respect to Y, and can
return a real value or a real matrix when evaluated.
Access: …µ
DIFFEQ
Input/Output: None
See also: AXES, CONIC, FUNCTION, PARAMETRIC, POLAR, RKFSTEP, RRKSTEP, TRUTH
DIR
Type: Function
Description: Creates an empty directory structure in run mode. Can be used as an alternative to CRDIR to
create an empty directory by typing DIR 'NAME' STO, which will create an empty directory
'NAME' if it does not already exist in the current directory.
Access: …µDIR
Input/Output:
Level 1/Argument 1 Level 1/Item 1
→
DIR …END
See also: CRDIR
DISP
Type: Command
Description: Display Command: Displays obj in the nth display line.
n ≤ 1 indicates the top line of the display.
To facilitate the display of messages, strings are displayed without the surrounding " " delimiters.
All other objects are displayed in the same form as would be used if the object were in level 1 in
the multiline display format. If the object display requires more than one display line, the display
starts in line n, and continues down the display either to the end of the object or the bottom of
the display. The object displayed by DISP persists in the display only until the keyboard is ready