Error in ppois function (PR#161)

ripley  writes:

On Fri, 9 Apr 1999 ihaka@stat.auckland.ac.nz wrote:

On Fri, 9 Apr 1999, Prof Brian D Ripley wrote:

     ppois(q, lambda)

where q is undefined! It should only be defined for integers. Similarly, x
should only be integers.

Ummmm.  I guess I see the argument for dpois, but I thought the
distribution function was defined for all values.  Wouldn't it be in order
to apply the integer argument function to floor(q) perhaps?

Try reading on:

It seems better to make ppois defined as the CDF for all q. The code

had

   x = floor(x + 0.5);

and that should be something like floor(x + 1e-7).

(q in R is x in C.)

This seems to be what S does.

ppois(1.5, 2)

[1] 0.4060058

ppois(1.1, 2)

[1] 0.4060058

and R-0.64.1 does

ppois(1.5, 2)

[1] 0.4060058

ppois(1.1, 2)

[1] 0.4060058

dpois(1.1, 2)

Warning: non-integer x = 1.100000
[1] 0

Happy?