I am able to create my desired chart using ggplot using the following code:
ggplot(data, aes(x=as.Date(data$Date, "%d/%m/%Y"), y=items)) + geom_col(fill="#00cccc")
However, when i use it with my full code, i get an error that reads "StartTag:invalid element name [68]"
my_pres<-
# Load template
read_pptx("C:/Users/USERNAME/Desktop/template.pptx") %>%
# 02 - SLIDE
add_slide(layout="Title with Subtitle and Content", master="MySlides2016") %>%
# 02 - Title
ph_with_text(type = "title", str = "Items by Day") %>%
# 02 - Chart
ph_with_vg_at(code = ggplot(data, aes(x=as.Date(data$Date, "%d/%m/%Y"), y=items)) + geom_col(fill="#00cccc"),left = 1, top = 2, width = 6, height = 4)