matlab code for mixture help

I have this code

mixtrue.dist='Exponential';

mixtrue.K=2;

mixtrue.weight=[0.1 0.9];

mixtrue.par=[1 10];

data=simulate(mixtrue,1000);

data.Strue=data.S;

data=rmfield(data,'S');

dataplot(data)

But i want to change the data given from simulate mixture i.e(data=simulate(mixtrue,1000))by

data I will insert .

How can I do this ?