TF from response graph

can any one know how to get transfer function from a response graph

Answer 1

[Abhishek Gupte]

I assume that you have the frequency response data for a system and want to get the Transfer Function coefficients for the system. try using the INVFREQS function.

[Krishna Kanth]

Thanks Abhishek for your answer... I had a response graph from which i need to find the system paramters.

[Walter Roberson]

What form is the graph in? If it is in handle graphics form,

plothand = findobj('type','line');

wd = get(plothand,'XData')

hd = get(plothand,'YData')

However, I see that invfreqs expects to have complex responses input in to it, but it is not possible for the XData or YData to come out complex. You would have to figure out how to deduce the complex response from the graph.