help in subs command in matlab

[mina.nms]

hello
i use subs command in my matlab programm:
i want to get F in numerical mode,F obtained from integral of f1/f2 in x variable
F=int(f1/f2,x);
I defined all the parameters like f1 and f2 in matlab program
but when i use subs command for getting F in numerical mode :
F=subs(F)
it gives me:

80000000/53*x-218939624984787810945868258845088449029409738928195994223102616160758771002292633056640625/51480725643981820379365740530823251026023781234881697313173028858080963557938025201664*sum((424000000*_R+602145919332786096773206130150045/2475880078570760549798248448)/(-10485760+786432000000*_R-19660800000000000*_R^2+163840000000000000000*_R^3)*log(x-_R),_R = RootOf(1289607252460968707743884122788697729404866442544234117653735297560364647529973909273735233219363120040937280920415858961-16139061738043178685349494825018824214560661205182646955191620978379047637605257466435283458000861446474394824829671833600000*_Z+605214815176619200700606055938205908046024795194349260819685786689214286410197154991323129675032304242789805931112693760000000000*_Z^2-10086913586276986678343434265636765134100413253239154346994763111486904773503285916522052161250538404046496765518544896000000000000000*_Z^3+63043209914231166739646464160229782088127582832744714668717269446793154834395536978262826007815865025290604784490905600000000000000000000*_Z^4))

what is Z and R here?

 

[Fractional-N]

Well, I don't know what are _Z and _R, but maybe it is better to write the subs command as below

F=subs(F,x,2)

The above expression assigns to syms variable "x" the value of "2" in "F" function