x-axis date limits on graph not as specified

[JeffF]

I thought I was getting a decent handle on working with dates. I have set start and end dates as 2022-04-20 and 2022-09-01, respectively. However, the chart appears to have them as 2022-04-13 and 2022-09-08. Not sure why. The text and legend positioning are off a bit too. However, I thought I would deal with that in a separate post once I have the limits working as desired.

library(tidyverse)
library("lubridate")
#> Loading required package: timechange
#> 
#> Attaching package: 'lubridate'
#> The following objects are masked from 'package:base':
#> 
#>     date, intersect, setdiff, union
library("reprex")
 

start_date <- ymd("2022-04-20")
end_date <- ymd("2022-09-01")
position_date <- ymd("2022-07-27") #place on x-axis

date_length <-days(start_date %--% end_date )
position_date_len <- days(start_date %--% position_date)
relative_date <- position_date_len/date_length

start_date
#> [1] "2022-04-20"
end_date
#> [1] "2022-09-01"
position_date
#> [1] "2022-07-27"

date_length
#> [1] "11577600d 0H 0M 0S"
position_date_len
#> [1] "8467200d 0H 0M 0S"
relative_date
#> [1] 0.7313433

turtle_activity_gtm <-  read_csv("https://www.dropbox.com/s/ujdyzqc74152325/turtle_activity_report.csv?dl=1")
#> Rows: 925 Columns: 62
#> ── Column specification ────────────────────────────────────────────────────────
#> Delimiter: ","
#> chr  (22): beach, county, activity, ref_no, activity_comments, encountered?,...
#> dbl  (31): uid, activity_no, nest_no, year, month, week, dayofyear, julianda...
#> lgl   (6): final_treatment, light_management, relocation_reason, lost_nest, ...
#> date  (3): activity_date, emerge_date, inventory_date
#> 
#> ℹ Use `spec()` to retrieve the full column specification for this data.
#> ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

ggplot(data = (turtle_activity_gtm |> filter(activity=="N"))) + 
  geom_bar(aes(x = activity_date, fill = species),
           position = position_dodge2(preserve = "single")) +
  scale_y_continuous(breaks = 1:12) +
  scale_x_date(date_breaks = "8 day", 
               date_labels = "%m/%d",
               date_minor_breaks = "1 day",
               limits = c( start_date, end_date))                                 +
    labs(x="",y="Number of Nests", title="Sea Turtle Nests", caption=' ') +
  theme(axis.text.y = element_text(face = "bold",  
                                   size = 10, angle = 0),
        axis.text.x = element_text(face = "bold",  
                                   size = 10, angle = -80),
        legend.position=c(x=relative_date, y=10/12),
        legend.justification = c(0, 1), #upper left
        legend.title = element_blank(),
        legend.spacing.x = unit(0, "mm"),
        legend.spacing.y = unit(0, "mm"),
        axis.title = element_text(size = 12, face = "bold"),
        plot.caption = element_text(size = 15)) +
  geom_text(x=ymd("2022-05-02"), y=8, hjust = "left",label="This is a test......")
#> Warning: Removed 1 rows containing non-finite values (`stat_count()`).

^{Created on 2023-01-11 with reprex v2.0.2}

Thanks,
Jeff

[scottyd22]

You can add expand = c(0, 0) to scale_x_date().

scale_x_date(date_breaks = "8 day", 
               date_labels = "%m/%d",
               date_minor_breaks = "1 day",
               limits = c(start_date, end_date),
               expand = c(0,0)
               ) +

[JeffF]

Yes, that works well. It even takes care of the placement of the text and legend along the x-axis.

I do have a follow-up question on the coordinates for expand = c(0,0). What are coordinate types? I tried integers or dates getting only errors.

Thanks,
Jeff

[scottyd22]

Glad to hear it worked! You should be able to enter integer values into the vector, and they will be applied as either a multiplicative and/or an additive expansion factor(s). Below is a link to further examples and explanations.

https://ggplot2.tidyverse.org/reference/expansion.html

[JeffF]

Me again with another follow-up. How come the x-axis labeling starts at 4/22 not 4/20?

[scottyd22]

I'm not exactly sure why it doesn't start at the minimum limit (or show the max). If you want to force the limits to show, you can replace date_breaks with breaks below. The end date was not picked up in the 8-day sequence, so I added it to the end of the vector.

scale_x_date(breaks = c(seq.Date(as.Date(start_date), as.Date(end_date), by = '8 days'), end_date),
             date_labels = "%m/%d",
             date_minor_breaks = "1 day",
             limits = c(start_date, end_date),
             expand = c(0,0)
             ) +

[JeffF]

Thanks again. After this recommendation and some play around on my own, I figured out how to place the legend, particularly relative to the y-axis, where I wanted it. In this case I wanted it at 10. I was always off a bit since there were those spaces above and below the limits.

scale_y_continuous(breaks = 0:12, expand = c(0,0)) +
  expand_limits(y = c(-.1, 12)) +

Here's my complete setup now.

library(tidyverse)
library("lubridate")
#> Loading required package: timechange
#> 
#> Attaching package: 'lubridate'
#> The following objects are masked from 'package:base':
#> 
#>     date, intersect, setdiff, union
library("reprex")
 

start_date <- ymd("2022-04-20")
end_date <- ymd("2022-09-01")
position_date <- ymd("2022-07-27") #place on x-axis

date_length <-days(start_date %--% end_date )
position_date_len <- days(start_date %--% position_date)
relative_date <- position_date_len/date_length
rel_y <- 10/12

start_date
#> [1] "2022-04-20"
end_date
#> [1] "2022-09-01"
position_date
#> [1] "2022-07-27"

date_length
#> [1] "11577600d 0H 0M 0S"
position_date_len
#> [1] "8467200d 0H 0M 0S"
relative_date
#> [1] 0.7313433
rel_y
#> [1] 0.8333333

turtle_activity_gtm <-  read_csv("https://www.dropbox.com/s/ujdyzqc74152325/turtle_activity_report.csv?dl=1")
#> Rows: 925 Columns: 62
#> ── Column specification ────────────────────────────────────────────────────────
#> Delimiter: ","
#> chr  (22): beach, county, activity, ref_no, activity_comments, encountered?,...
#> dbl  (31): uid, activity_no, nest_no, year, month, week, dayofyear, julianda...
#> lgl   (6): final_treatment, light_management, relocation_reason, lost_nest, ...
#> date  (3): activity_date, emerge_date, inventory_date
#> 
#> ℹ Use `spec()` to retrieve the full column specification for this data.
#> ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

ggplot(data = (turtle_activity_gtm |> filter(activity=="N"))) + 
  geom_bar(aes(x = activity_date, fill = species),
           na.rm = TRUE,
           position = position_dodge2(preserve = "single")) +
  scale_y_continuous(breaks = 0:12, expand = c(0,0)) +
  expand_limits(y = c(-.1, 12)) +
  scale_x_date(breaks = c(seq.Date((start_date), (end_date), 
                                   by = '5 days'), end_date), 
               date_labels = "%m/%d",
               date_minor_breaks = "1 day",
               limits = c( start_date, end_date),
               expand = c(0,0))   +
  labs(x="",y="Number of Nests", title="Sea Turtle Nests", caption=' ') +
  theme(axis.text.y = element_text(face = "bold",  
                                   size = 10, angle = 0),
        axis.text.x = element_text(face = "bold",  
                                   size = 10, angle = -80),
        legend.position=c(x=relative_date, y=rel_y),
        legend.justification = c(0, 1), #upper left
        legend.title = element_blank(),
        axis.title = element_text(size = 12, face = "bold"),
        plot.caption = element_text(size = 15)) +
  geom_text(x=ymd("2022-05-02"), y=8, hjust = "left",label="This is a test......")

^{Created on 2023-01-11 with reprex v2.0.2}