[R-sig-Geo] Plotting median values globally

[r@i@1290 m@iii@g oii @im@com]

Hi there,
I am trying to create a global plot with median precipitation values. What I would like to do is isolate the "median" values and plot those values on a global raster map. I already first created a raster stack, called "RCP1pctCO2median", which contains the median values to be plotted. However, what I would like to do is simply plot only those values at Year 61 for each grid cell. There are 138 layers, with each layer representing one year. The idea would be to plot only those values for Year/layer 61 globally (i,e, for each grid cell), but I am unsure how to isolate that specific year/layer? 
"RCP1pctCO2median"  has the following attributes:

class       : RasterStack 
dimensions  : 64, 128, 8192, 138  (nrow, ncol, ncell, nlayers)
resolution  : 2.8125, 2.789327  (x, y)
extent      : -181.4062, 178.5938, -89.25846, 89.25846  (xmin, xmax, ymin, ymax)
coord. ref. : +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0 
names       :    layer.1,    layer.2,    layer.3,    layer.4,    layer.5,    layer.6,    layer.7,    layer.8,    layer.9,   layer.10,   layer.11,   layer.12,   layer.13,   layer.14,   layer.15, ... 
min values  : 0.42964514, 0.43375653, 0.51749371, 0.50838983, 0.45366730, 0.53099146, 0.49757186, 0.45697752, 0.41382199, 0.46082401, 0.45516687, 0.51857087, 0.41005131, 0.45956529, 0.47497867, ... 
max values  :   96.30350,  104.08584,   88.92751,   97.49373,   89.57201,   90.58570,   86.67651,   88.33519,   96.94720,  101.58247,   96.07792,   93.21948,   99.59785,   94.26218,   90.62138, ... 


And this is how I would like to create my global raster map. However, I am not sure how to plot only one value (i.e. the median value, which occurs at Year 61) for each grid cell. This is what I have so far, but all that this does is plot 138 mini plots, and I just want one plot showing the median values (i.e. Year 61):


mapTheme<-rasterTheme(region=rev(brewer.pal(10,"Spectral")))
cutpoints<-c(200,175,150,125,100,75,50,25,0)
levelplot(RCP1pctCO2median,margin=F,at=cutpoints,cuts=11,pretty=TRUE,par.settings=mapTheme, main="Median values")



Any help would be greatly appreciated!
I look forward to your response! 
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