Scatter graph formatting help in R

[quezi]

Hello all,
I'm currently doing a project which I'm trying to use R with to get more familiar with it.

I've run into a problem with scatter graphs. The one below, for example, shows the area of occurrence/occupancy of individual species within a genus of marine organism plotted against the year each species was discovered, with a gradual decrease in the area of occupancy over time.
However, the 0 on the y axis starts a little bit high up the axis, leaving a white band right at the bottom. Also, the regression line carries on below zero - clearly it is impossible for a species to occupy an area of habitat less than zero.

So my questions - is there a way to stop the regression line from continuing below zero, and is there a way to shift all datapoints and the start of the axis downwards slightly to remove this blank 'band'?

Thanks.

 

[chetan.apa]

As per my understanding, I do not think there is anything wrong with the R scatter plot. When you run your regression, it does not guarantee about the range of predicted/fitted values, even if your independent variable is positive, the predicted/fitted can be negative.
Because of this you are getting a blank 'band'.

Still if you want I think the plotting of red line can be controlled..just plot points which are positive. May be you could provide us the attempted code and data..