[SOLVED] how to convert discrete time to continuous time in matlab

[meliasamad]

hi,
i want to convert discrete time to continuous time to get a state space model. how can i done it?
this is my discrete time arx model

arx20201 =
Discrete-time ARX model: A(z)y(t) = B(z)u(t) + e(t)

A(z) = 1 - 1.247 (+/- 0.2965) z^-1 + 0.7432 (+/- 0.4742) z^-2 - 0.3961 (+/- 0.524) z^-3
- 0.006099 (+/- 0.5932) z^-4 + 0.6106 (+/- 0.5883) z^-5 - 0.7177 (+/- 0.5875) z^-6
+ 0.5505 (+/- 0.6619) z^-7 - 0.1075 (+/- 0.6721) z^-8 - 0.3649 (+/- 0.6704) z^-9
+ 0.7091 (+/- 0.6878) z^-10 - 0.5869 (+/- 0.6481) z^-11 + 0.7063 (+/- 0.7207) z^-12
- 0.5783 (+/- 0.8296) z^-13 + 0.168 (+/- 0.751) z^-14 + 0.119 (+/- 0.7357) z^-15
- 0.06076 (+/- 0.752) z^-16 + 0.2342 (+/- 0.7625) z^-17 - 0.1151 (+/- 0.7954) z^-18
- 0.03145 (+/- 0.7588) z^-19 - 0.08367 (+/- 0.4427) z^-20


B(z) = -0.0001474 (+/- 0.0003177) z^-1 - 0.0001641 (+/- 0.0003064) z^-2 - 0.0001606 (+/
- 0.0002768) z^-3 - 5.961e-05 (+/- 0.0002344) z^-4 - 0.0001216 (+/- 0.0002887) z^-5
+ 6.736e-06 (+/- 0.0003786) z^-6 - 0.000631 (+/- 0.0005666) z^-7 - 0.0004827 (+
/- 0.0006123) z^-8 - 0.0008252 (+/- 0.0004958) z^-9 - 0.0001782 (+/- 0.0003717) z^-10
- 0.0003097 (+/- 0.0003552) z^-11 - 0.000537 (+/- 0.0003531) z^-12 - 0.0004731 (
+/- 0.0003576) z^-13 - 0.000393 (+/- 0.0003763) z^-14 - 0.0002854 (+/- 0.0004366) z^-15
+ 0.0002117 (+/- 0.0005339) z^-16 + 0.0002379 (+/- 0.0005108) z^-17 + 0.0001983 (
+/- 0.0004116) z^-18 + 0.0002264 (+/- 0.0003036) z^-19 + 0.000102 (+/- 0.0002864) z^-20