Function for formatting and plotting in R - r

Question

I am currently trying to create a function that will format my data and properly and return a bar plot that is sorted. Yet for some reason I keep getting this error:
Error in `$<-.data.frame`(`*tmp*`, "Var1", value = integer(0)) :
replacement has 0 rows, data has 3
I have tried debugging it, but have had no luck. I have an example of what I expect down at the bottom. Can anyone spot what I am doing wrong?
x <- rep(c("Mark","Jimmy","Jones","Jones","Jones","Jimmy"),2)
y <- rnorm(12)
df <- data.frame(x,y)
plottingfunction <- function(data, name,xlabel,ylabel,header){
newDf <- data.frame(table(data))
order <- newDf[order(newDf$Freq, decreasing = FALSE), ]$Var1
newDf$Var1 <- factor(newDf$Var1,order)
colnames(newDf)[1] <- name
plot <- ggplot(newDf, aes(x=name, y=Freq)) +
xlab(xlabel) +
ylab(ylabel) +
ggtitle(header) +
geom_bar(stat="identity", fill="lightblue", colour="black") +
coord_flip()
return(plot)
}
plottingfunction(df$x, "names","xlabel","ylabel","header")

Answer 1

A few comments, your function didn't work, because this part isn't correct:
order <- newDf[order(newDf$Freq, decreasing = FALSE), ]$Var1
Since we have no idea if there will be any columns in data which has the column name Var1. What looks like happend is when you were trying your code you ran:
newDf <- data.frame(table(df$x))
which immediately renamed your column to Var1, but when you ran your function, the name changed. So to get around this I would recommend being explicit with your column names. In this example, I used the dplyr library to make my life easier. So following your code and logic it would look like this:
newDf <- data %>% group_by_(col_name) %>% tally
order <- newDf[order(newDf$n, decreasing = FALSE), col_name][[col_name]]
data[,col_name] <- factor(data[,col_name], order)
Then within your ggplot we can use aes_string to refer to the column name of the data frame instead. So then the whole function would look like this:
plottingFunction <- function(data, col_name, xlabel, ylabel, header) {
#' create a dataframe with the data that we're interested in
#' make sure that you preserve the anme of the column that you're
#' counting on...
newDf <- data %>% group_by_(col_name) %>% tally
order <- newDf[order(newDf$n, decreasing = FALSE), col_name][[col_name]]
data[,col_name] <- factor(data[,col_name], order)
plot <- ggplot(data, aes_string(col_name)) +
xlab(xlabel) +
ylab(ylabel) +
ggtitle(header) +
geom_bar(fill="lightblue", colour="black") +
coord_flip()
return(plot)
}
plottingFunction(df, "x", "xlabel","ylabel","header")
Which would have output like:
I think for your plot having stat="identity" is redundant since you can just use your original data frame rather than having a transformed one.