[R] Distribution fitting problem

[Mark Miller]

I am using the MASS library function 

fitdistr(x, dpois, list(lambda=2))

but I get 

Error in optim(start, mylogfn, x = x, hessian = TRUE, ...) :
        Function cannot be evaluated at initial parameters
In addition: There were 50 or more warnings (use warnings() to see the first 
50)

and all the first 50 warnings say 

1:  non-integer x = 1.452222
etc

Can anyone tell me what I am doing wrong. p.s. the data was read in from 
a .csv file that I wrote using octave