Comparison of eXpress and RNA-Skim

library(ggplot2)
setwd("~/hydrogen/sorghum/mrna")
# express
express <- read.table("express_BS-1/results.xprs", sep="\t", header=T)

express <- express[,c(2,15)]
names(express) <- c("target_id", "express.tpm")
# rna-skim
skim <- read.table("rnaskim_BS-1/expression", sep="\t", header=F)
skim <- skim[,c(1,5)]
names(skim) <- c("target_id", "skim.tpm")

# merge
data <- merge(x=express, y=skim, by="target_id", all.x=F, all.y=F)

correlation <- cor(data[,c(2,3)])
head(correlation)
##             express.tpm skim.tpm
## express.tpm      1.0000   0.9714
## skim.tpm         0.9714   1.0000

Scatter:

ggplot(data, aes(x=express.tpm, y=skim.tpm)) +
  geom_point(shape=19,
             size = 3,
             alpha = I(0.4)) +
  coord_fixed(ratio = 1, xlim=c(-1,1000), ylim=c(-1,1000))

plot of chunk unnamed-chunk-2

Density:

library(reshape2)
data2 <- data[data$express.tpm>0.001,]
data2 <- data2[data2$skim.tpm>0.001,]

melt <- melt(data2, id = "target_id")
ggplot(data = melt, aes(x = log(value), colour = variable)) + geom_density()

plot of chunk unnamed-chunk-3

filter <- data[data$skim.tpm>600,]
filter <- filter[filter$express.tpm<20,]
head(filter)
##          target_id express.tpm skim.tpm
## 601  Sb01g004330.2      13.625    812.7
## 1077 Sb01g008420.2       6.446    643.8
## 7824 Sb02g032090.1      17.454   1282.8