HP 50g Graphing manual Programmatic Use of Statistics and Plotting, Techniques used in PIE

Programmatic Use of Statistics and Plotting

This section describes a program PIE you can use to draw pie charts. PIE prompts for single variable data, stores that data in the statistics matrix ΣDAT, then draws a labeled pie chart that shows each data point as a percentage of the total.

Techniques used in PIE

Programmatic use of PLOT commands. PIE executes XRNG and YRNG to define x and yaxis display ranges in user units, and executes ARC and LINE to draw the circle and individual slices.

Programmatic use of matrices and statistics commands.

Manipulating graphics objects. PIE recalls PICT to the stack and executes GOR to merge the label for each slice with the plot.

FOR…NEXT (definite loop). Each slice is calculated, drawn, and labeled in a definite loop.

CASE…END structure. To avoid overwriting the circle, each label is offset from the midpoint of the arc of the slice. The offset for each label depends on the position of the slice in the circle. The CASE…END structure assigns an offset to the label based on the position of the slice.

Preserving calculator flag status. Before specifying Radians mode, PIE saves the current flag status in a local variable, then restores that status at the end of the program.

Nested local variable structures. At different parts of the process, intermediate results are saved in local variables for convenient recall as needed.

Temporary menu for data input.

PIE program listing

Program:	Comments:
«
RCLF → flags	Recalls the current flag status and
	stores it in variable flags.
«
RAD	Sets Radians mode.
{{ "SLICE" Σ+ }	Defines the input menu: key 1
{ }	executes Σ+ to store each data point
{ "CLEAR" CLΣ }	in ΣDAT, key 3 clears ΣDAT, and
{ } { }	key 6 continues program execution
{ "DRAW" CONT }}
	after data entry.
TMENU	Displays the temporary menu.
"Key values into	Prompts for inputs.
SLICE,DRAW	represents the newline character
restarts program."	(… Ë) after you enter the
PROMPT
	program on the stack.
ERASE 1 131 XRNG	Erases the current PICT and sets plot
1 64 YRNG CLLCD	parameters.
"Please wait...	Displays “drawing” message.
Drawing Pie Chart"
1 DISP

234 RPL Programming Examples