 Dear Rexperts,

 I am trying to add a '+' identifying the mean in a boxplot using the
   following
   sizelist <- split(size, grp)
   centers <- boxplot(sizelist, style.bxp = "att", medpch = "o",
       ylab = "Prostate Volume (cm3)")
   points(centers, unlist(lapply(sizelist, mean)), pch = "+")
   But, I get error
   Error in xy.coords(x, y) : 'x' and 'y' lengths differ
   which I do not understand.
   The data follows
   grp    size
   AE    9.132
   AE    10.07
   AE    20.077
   AE    14.691
   AE    23.698
   E1    10.356
   E1    6.313
   E1    21.708
   E1    12.651
   E1    15.464
   E2    37.2
   E2    12.639
   E2    16.791
   E2    36.996
   E2    22.808
   CC    1.975
   CC    3.125
   CC    4.433
   CC    6.154
   CC    4.175
   NC    9.301
   NC    13.531
   NC    12.84
   NC    14.336
   NC    25.102

   Please help.

-- 
Oscar
Oscar A. Linares, MD
Translational Medicine Unit
LaPlaisance Bay, Bolles Harbor
Monroe, Michigan 48161

Department of Medicine,
University of Toledo College of Medicine
Toledo, OH 43606-3390

Department of Internal Medicine,
The Detroit Medical Center (DMC)
Harper University Hospital
Wayne State University School of Medicine
Detroit, Michigan 48201

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