Holt-Winters to predict next month data with previous 6 months data

[Raina Mortuja]

Hi,

I have sales data from January to June and I want to predict the sales for July using Holt-Winters. I have written a R script that works for monthly data if I have data for an entire year but it does not work for a dataset of 6 months.

I have attached the script and error received to this question.

I would very much appreciate the help.

thanks!