self-organizing map in R

July 19, 2012

(This article was first published on One Tip Per Day, and kindly contributed to R-bloggers)

This is my first SOM figure 🙂
Thanks to the som package and example code from Jun Yan. Here is my code for the figure:

rpkm <- Tx_rpkm[, -c(1:4)]
rpkm.f <- filtering(rpkm, lt=10, ut=30000, mmr=2, mmd=10)
# rpkm.f=log(rpkm.f+0.1) # this doesn’t really change much of the result
rpkm.f.n <- normalize(rpkm.f)
foo <- som(rpkm.f.n, xdim=5, ydim=5, topol=”rect”, neigh=”bubble”)
png(“../results/clustering.SOM.RNAseq.png”,width=800, height=800)
plot(foo,yadj=0.15, main=”Expression profiles obtained by self-organizing map (SOM) clustering \nof individual mRNA transcript throughout the time-course”, xlab=”Stage: D13 – D14 – D15 – D16 – D17 – D18″)
I am still not very clear how to choose the proper xdim and ydim. Also, what’s the color code for the bar mean?  Hope anyone know SOM could leave comment here. Or, I will read article myself 🙂
Is the normalization necessary?

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