In oreder to compare Impulse Invariance method charactristics for transformation analogue filters to digital ones in highpass and bandpass and lowpass formats,here are 6 M-files that simulate a third order butterworth filter analyizing impulse response(time domain) and frequency analysis of analogue and transformed digital filters-In oreder to compare Impulse Invariance method charactristics for transformation analogue filters to digital ones in highpass and bandpass and lowpass formats,here are 6 M-files that simulate a third order butterworth filter analyizing impulse response(time domain) and frequency analysis of analogue and　transformed digital filters