**HP Prime: Slopefield (Differential Equations)**

Here is a program that graphs the slopefield of a
differential equation in the form dy/dx = f(x,y). This program is adopted from Alan Ziv’s
SLPFIELD program, which Ziv programmed for the Casio fx-9850G. The link to the original program is
here: http://www.spiderpixel.co.uk/caspro/progs/9x50g/slopefield.txt

For the HP Prime version, enter dy/dx in quotes, and use
capital letters X and Y. I recommend that
you are in the Function app for this.
The window should be set up before running SLOPEFIELD.

**Program SLOPEFIELD**

EXPORT SLOPEFIELD(dxy)

BEGIN

// dxy: dx/dy = f′(x,y)

// Adopted from Alan Ziv -

// Casio

// dxy is in quotes

LOCAL X,Y,C,D,J,K,G,H;

LOCAL F,xa,xb,ya,yb,E;

// Use the Function App

RECT();

C:=(Ymax-Ymin)/220;

D:=(Xmax-Xmin)/320;

FOR J FROM 0 TO 50 DO

E:=Xmin+(8*J+3)*D;

FOR K FROM 0 TO 27 DO

F:=Ymin+(8*K+3)*C;

X:=E;

Y:=F;

G:=EXPR(dxy);

H:=2*D;

IF ABS(G)>C/D THEN

H:=2*C/ABS(G);

END;

IF 2*H>D THEN

xa:=E-H; ya:=G*(xa-E)+F;

xb:=E+H; yb:=G*(xb-E)+F;

LINE(xa,ya,xb,yb);

ELSE

LINE(E,F+2*C,E,F-2*C);

END;

END;

END;

// Draw Axis

LINE(Xmin,0,Xmax,0,#C0C0C0h);

LINE(0,Ymin,0,Ymax,#C0C0C0h);

WAIT(0);

END;

dy/dx = X*^Y^2 + 3*X |

This blog is property of Edward Shore. 2015

## No comments:

## Post a Comment