[R-sig-Geo] How to draw two variogram curves in one plot

[lwwhdz]

Dear all
     I am doing some work on regression kriging in R. Now I want to plot the varigrom curves of the dependent variable (A) and the regression residuals (B) before kriging. With this plot, I can easily to compare the autocorrelation (e.g. sill, range & nugget) of A and B.  I tried the following two commond, but it failed. 
......
plot(variogram(A~1,data), vgm_a,  pch = 19, col = "black", lwd=2, add=TRUE) 
plot(variogram(B~1,data), vgm_b,  pch = 19, col = "black", lwd=2) 
......
    Is there anyone have any ideas? Thanks very much!



Wang Li
Phd Candidate in University of Chinese Academy of Sciences (UCAS) and Institute of Remote Sensing and Digital Earth, CAS,The State Key Laboratory of Remote Sensing Science
CAS Olympic S&T Park, No. 20 at Datun Road, Chaoyang, Beijing, P.R.C. (P. O. Box 9718)
lwwhdz at sina.com
lwwhdz at gmail.com
(+86)18810433086

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