I wanted to make a function to take another function that takes a 2d-vector and returns a 2d-vector, x and y boundaries, and a resolution, and plot the slope field. However all I get is a blank plot over a small range and some vertical and horizontal lines. This is my code, if you know differential equations with the function I'm using you should see a saddle at the origin and a center at 1,1. import matplotlib.pyplot as plt def plot_system(function, xmin, xmax, ymin, ymax, resolution): xnow = xmin i = 0 while xnow < xmax: ynow = ymin while ynow < ymax: direction = function([xnow, ynow]) if direction[0]**2 + direction[1]**2 != 0: scale = resolution / (direction[0]**2 + direction[1]**2)**.5 print repr(direction[0] * scale) + ", " + repr(direction[1] * scale) plt.arrow(xnow, ynow, direction[0] * scale, direction[1] * scale) ynow = ynow + resolution xnow = xnow + resolution print "plotting" plt.show() if __name__ == "__main__": def function(y): return [y[0] - y[0]*y[1], y[0]*y[1] - y[1]] plot_system(function, -10, 10, -10, 10, 1) -- View this message in context: http://www.nabble.com/Arrows-acting-funny-tp20713470p20713470.html Sent from the matplotlib - users mailing list archive at Nabble.com.