spec1<-read.table("fa1-ir.txt.out")
names(spec1)<-c("1/cm","absorb")
spec2<-read.table("fa2-ir.txt.out")
names(spec2)<-c("1/cm","absorb")
spec3<-read.table("fa3-ir.txt.out")
names(spec3)<-c("1/cm","absorb")

d.spec1<-diff(spec1$absorb)
d2.spec1<-diff(d.spec1)

d.spec2<-diff(spec2$absorb)
d2.spec2<-diff(d.spec2)

d.spec3<-diff(spec3$absorb)
d2.spec3<-diff(d.spec3)

par(mfcol=c(3,1))
plot(spec1,type="l")
lines(spec2, col="red")
lines(spec3, col="blue")
plot(d.spec1,type="l")
lines(d.spec2, col="red")
lines(d.spec3, col="blue")
plot(d2.spec1,type="l")
lines(d2.spec2, col="red")
lines(d2.spec3, col="blue")