Dear List:
I cannot seem to find a way to plot my data correctly. I have a small data frame with
6 total variables (x_1 ... x_6).
I am trying to plot x_1 against x_2 and x_3.
I have tried
plot(x_2, x_1) #obviously works fine
plot(x_3, x_1, add=TRUE) # Does not work. I keep getting error messages.
I would also like to add ablines to this plot.
I have experimented with a number of other plotting functions and I cannot seem to get
this to work.
The data are student achievement data. I am trying to plot percentile ranks against
scale scores for different grade levels. When plotted as such, they look like logistic
curves. I am trying to show graphically the distance along x a student must grow
simply to remain at the same percentile rank, y.
Thanks.
Harold C. Doran
One Massachusetts Avenue, NW � Suite 700
Washington, DC 20001-1431
202.336.7075
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