Line chart uses week number for x-axis but uses month name as label

Question

I have a dataframe with 4 columns. This includes year, month, week_no (week of the year), and a count field (n).

I want to plot a line graph showing the number of starts by year, with a individual line for each year. The x-axis would would use the week number field, but would be labelled using the month, so it would produce something like the below:

year	month	week number	starts
2021	Dec	50	101
2021	Dec	51	104
2021	Dec	52	110
2022	Jan	1	111
2022	Jan	2	115
2022	Jan	3	144
2022	Jan	4	156

I have used the below code in plotly but this displays the week number on the x-axis

plot_ly(df, x = ~week_number, y = ~starts  type = 'scatter',color = ~year, mode = 'lines')

Answer 1

I have made an adjustment to the data, to put all the dates near December, so the plot looks better for this small portion of dataset. See below;

All you need to do is changing ticktext using layout :

library(plotly)

plot_ly(df1, x = ~week_number, y = ~starts,  
            type = 'scatter', color=~as.character(year), mode = 'lines') %>% 
  layout(xaxis = list(tickvals = ~week_number, ticktext = ~month))

Update:

In order to get a tick mark for every month, we need actual dates, not just week number. You can convert a date formatted as YYYY-UU-uu to the conventional date format. However, here since you want all years to appear on top of each other, we should a arbitrary year for all the rows, so the plot won't get extended to multiple years.

After mutating those dates, we can use layout to set the dtick to M1 and format the labels as %b to only show the month names once. ticklabelmode = 'period' makes sure to have a tick for every month. I added a hovertemplate to show the week number. I also removed the title from the axes and added a graph title to make the final plot closer to what you've shown in your question.

library(plotly)
library(dplyr)

df2 %>% 
  mutate(pseudo_Date = as.Date(paste(2000, week_number, 1, sep="-"), "%Y-%U-%u")) %>% 
 plot_ly(., x = ~pseudo_Date, y = ~starts,  
         type = 'scatter', color=~as.character(year), mode = 'lines',
         hovertemplate = "Week Number: %{x|%U | } %{x}") %>% 
  layout(xaxis = list(title = "", 
                      dtick = "M1", tickformat = '%b', ticklabelmode = "period"),
         yaxis = list(title = ""),
         title = 'Chart 2. Total starts by week')

Data:

df1 <- read.table(text = "year  month   week_number     starts
2021    Dec     50  101
2021    Dec     51  104
2021    Dec     52  110
2022    Nov     48  111
2022    Dec     49  115
2022    Dec     50  144
2022    Dec     51  156", header = T, stringsAsFactor = F)

df2 <- read.table(text = "year  month   week_number     starts
2020    Nov     46  100
2020    Nov     47  120
2020    Nov     48  111
2020    Dec     49  115
2020    Dec     50  144
2020    Dec     51  156
2021    Dec     50  101
2021    Dec     51  104
2021    Dec     52  110
2022    Jan     1   108
2022    Jan     2   108
2022    Jan     3   125
2022    Jan     4   160", header = T, stringsAsFactor = F)