[R] ggplot - class "character" problem

[David Menezes]

Hi

I'm trying to use ggplot2 to chart a dataset that I've drawn in from
excel.  When I run the qplot command, I get the following error
message:

Error: ggplot2 doesn't know how to deal with data of class character


It feels like I need to coerce one of the fields in my data frame.
Here's the code, which is short:

#draw data in from network location
setwd("S:\\790\\Actuarial\\KFC\\609 Kernel\\Sensitivity
Tests\\Stressed ESG inputs")
input<-read.csv("yieldcurve plus 1pct abs.csv",header=FALSE)

#label columns
colnames(input)<-c("scenID","yrs_ahead",0.5,1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0)

#create a data frame that i hope! will work with ggplot..
flat_data<-data.frame(cbind(input[1:2],stack(input[3:15])))
colnames(flat_data)<-c("scenID","yrs_ahead","yield","time")

#plot
library(ggplot2)
qplot(time,yield,data="flat_data",facets = yrs_ahead~.)

now the error.

In terms of the data format, head(flat data) returns the following:

> head(flat_data)
  scenID yrs_ahead      yield time
1      1         0 0.01637218  0.5
2      1         1 0.02446376  0.5
3      1         2 0.04501267  0.5
4      1         3 0.06947724  0.5
5      1         4 0.08262982  0.5
6      1         5 0.09761927  0.5

1) Am I right that it's about coercion of variable type?
2) Any ideas how to proceed?

Many thanks,
Dave