Attached is an picture of the result when the plugin is applied to the following window settings:

Xmin: -10         Ymin: -500
Xmax: 10          Ymax: 500
Tick Unit: 1        Tick Unit: 100
Grid Unit: 1        Grid Unit: 50

Copy the attached file to the plugin folder.

(4) n is odd (Non-Reflectional Symmetry)

Preview

(1) n is even

(2) n is odd

Preview

Install the plugin file slopefield.py in the plugins folder before starting Graph.

Shortcut to plot slope field is: Ctrl+Shift+S

Input dy/dx based on x and y. The rectangle to plot the slope field in is defined by x-min (a) , x-max (b) , y-min (c), and y-max (d).
Input the number of equal subdivisions for the x-interval (m), and the number of equal subdivisions for the y-interval (n).

      y' = f(x,y)   (a<x<b, c<y<d).

  * The interval [a,b] is divided into m equal subdivisions.
    Let x0, x1, x2, ..., xm be the endpoints of the subdivisions.

  * The interval [c,d] is divided into n equal subdivisions.
    Let y0, y1, y2, ..., yn be the endpoints of the subdivisions.

  * A small tangent segment is centered at each of the points
    (xi, yj), for i = 0, 1, 2, ..., m and j = 0, 1, 2, ..., n,
    showing the slope of the solution curve there.

  * The slope field consists of the (m+1)(n+1) tangent segments.

Zoom square to make the segments look equal in length.

***NOTE: Attachment #2 is updated to work with the latest Beta Build of Graph.