def exponential(x, y, xscale, yscale):
if xscale==<NUM_LIT:0.0> or yscale==<NUM_LIT:0.0>:<EOL><INDENT>return x*<NUM_LIT:0.0><EOL><DEDENT>with float_error_ignore():<EOL><INDENT>x_w = np.divide(x,xscale)<EOL>y_h = np.divide(y,yscale)<EOL>return np.exp(-np.sqrt(x_w*x_w+y_h*y_h))<EOL><DEDENT>
Two-dimensional oriented exponential decay pattern.