[R] Linear Regression with slope equals 0

[E.N.D.Grew at exeter.ac.uk]

 Hi there, am trying to run a linear regression with a slope of 0.

 I have a dataset as follows

 t d
 1 303
 2 302
 3 304
 4 306
 5 307
 6 303

 I would like to test the significance that these points would lie on a
horizontal straight line.

 The standard regression lm(d~t) doesn't seem to allow the slope to be set.

 Any help very welcome.

 ed