Newly created function is not found in working directory - r

Question

I replicate the code from here in order to create the HWplot() function with:
#HWplot.R
library(ggplot2)
library(reshape)
HWplot<-function(ts_object, n.ahead=4, CI=.95, error.ribbon='green', line.size=1){
hw_object<-HoltWinters(ts_object)
forecast<-predict(hw_object, n.ahead=n.ahead, prediction.interval=T, level=CI)
for_values<-data.frame(time=round(time(forecast), 3), value_forecast=as.data.frame(forecast)$fit, dev=as.data.frame(forecast)$upr-as.data.frame(forecast)$fit)
fitted_values<-data.frame(time=round(time(hw_object$fitted), 3), value_fitted=as.data.frame(hw_object$fitted)$xhat)
actual_values<-data.frame(time=round(time(hw_object$x), 3), Actual=c(hw_object$x))
graphset<-merge(actual_values, fitted_values, by='time', all=TRUE)
graphset<-merge(graphset, for_values, all=TRUE, by='time')
graphset[is.na(graphset$dev), ]$dev<-0
graphset$Fitted<-c(rep(NA, NROW(graphset)-(NROW(for_values) + NROW(fitted_values))), fitted_values$value_fitted, for_values$value_forecast)
graphset.melt<-melt(graphset[, c('time', 'Actual', 'Fitted')], id='time')
p<-ggplot(graphset.melt, aes(x=time, y=value)) + geom_ribbon(data=graphset, aes(x=time, y=Fitted, ymin=Fitted-dev, ymax=Fitted + dev), alpha=.2, fill=error.ribbon) + geom_line(aes(colour=variable), size=line.size) + geom_vline(x=max(actual_values$time), lty=2) + xlab('Time') + ylab('Value') + opts(legend.position='bottom') + scale_colour_hue('')
return(p)
}
The function seems to be created normally but when I try to load it using:
source("HWplot.R")
I get:
Error in file(filename, "r", encoding = encoding) :
cannot open the connection
In addition: Warning message:
In file(filename, "r", encoding = encoding) :
cannot open file 'HWplot.R': No such file or directory

Answer 1

If you run list.files(pattern='HWplot.R') what do you get?
character(0)
This means the file is not in the working directory, as evidenced by the error R was throwing:
cannot open file 'HWplot.R': No such file or directory
This could be due to 2 reasons.
1. File is actually not in working directory
You are calling source("HWplot.R"). This assumes that this file is in the working directory.
I would recommend doing getwd() and locating where you saved your HWplot.R file, they should be in the same directory if you want your source() command to work. As a general rule source(path/to/file).
You can also run list.files() to see what's actually in the directory.
2. Typo
Happened to me a million times. Check that the spelling of your R code and the file's name matches, otherwise it will never find it!