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 |
 |
| dy/dx = Y*SIN(X) |
This blog is property of Edward Shore. 2015
