Polynomial regression: how to plot several regression lines on same graph.

Hi there,

I am currently working on my thesis which is concerned with abnormality of differences between index scores on an intelligence test. An important factor here are the correlations between indexes. There are 4 indexes, hence 6 possible pairs. Correlations between indexes are provided for 13 age bands.

To investigate potential age effects on the correlations (and non-linear relationships) I carried out hierarchical multiple regression using polynomial functions of age (i.e. age_band, age_band_squared, age_band_cubed) as predictor variables and the correlation between a pair of indexes as dependent variable.

Example of regression equation: IndexA*IndexB = 0.2 + 0.13 x age - 0.02 x age_squared + 0.001 x age_cubed.

My supervisor now wants me to plot the regression lines of the 6 pairs of indexes all on one figure; with age as x-axis and correlation as y-axis. He doesn't want the actual data points in there but only the regression lines.

I tried to do this with SPSS, but can't work out how to plot different regression lines in the same graph.

Help would be greatly appreciated! Thanks!
have you used R? can do:

plot(x,y,type='n', ylim=c(ym,yM),xlim=c(xm,xM))

where ym,yM,xm,xM are the min's and max's of the plot regino
Thank you very much for your reply. I actually downloaded R today but I've never used it before. I find it quite difficult to make sense of it, but I'll give it a shot. This might be a stupid question, but do I have to carry out the regression before applying your commands? Thanks again :)