How to draw a line with different color and size

LineWithDifferentColorAndSize.r

library("ggplot2")

> x = c(1:10)
> y = c(1:10)
> colours = rainbow(10)
> size <- c(1,2,3,4,5,5,4,3,2,1)
> tt <- data.frame(x=x,y=y,colours=colours,size=size)
> tt

 x  y   colours size
1   1  1 #FF0000FF    1
2   2  2 #FF9900FF    2
3   3  3 #CCFF00FF    3
4   4  4 #33FF00FF    4
5   5  5 #00FF66FF    5
6   6  6 #00FFFFFF    5
7   7  7 #0066FFFF    4
8   8  8 #3300FFFF    3
9   9  9 #CC00FFFF    2
10 10 10 #FF0099FF    1

> ggplot(tt,aes(x=x,y=y,group=1,colour=colours,size=size)) + geom_line()
# The most important thing to remember is group=1 which meant all the points belongs to just one group.