Arrow on Nyquist plot

I'd like to draw Nyquist plot with the arrow going from high frequency to low frequency (i.e, opposite direction as it is by default). Is it possible? It this is not possible, I'd rather not have the arrow on the curve, is this possible?

Answer 1

[Anna]

I use the nyquist command and I get the nyquist plot with the arrow going from low frequency to high frequecny. I'd like to have the arrow point the other way, instead.

Answer 2

[Kwin]

Assuming a rational transfer function with real coefficients, then this can be done by inputting the complex conjugate of the original transfer function. This can be achieved by multiply each coefficient of odd powers of s by minus one. So for example:

>> figure, nyquist(tf([1 1],[1 1 2 0]))
>> figure, nyquist(tf([-1 1],[-1 1 -2 0]))

yields the same plots, but with the arrows pointing in the opposite direction.