[R] Lines in a line graph not visible when values are identical

[Rui Barradas]

Hello,

What if instead of colors, you facet the plot by Year?


ggplot(DF, aes(x = Parameter, y = Millimetres, group = Year)) +
  geom_line(linewidth = 1) +
  geom_point(size = 2) +
  labs(
    title = "Parameters by Year",
    x = "Parameter",
    y = "Millimetres ($)"
  ) +
  facet_wrap(~ Year) +
  theme_minimal()


Also, the data in dput format.

DF <-
structure(list(Parameter = structure(c(1L, 2L, 3L, 4L, 1L, 2L,
3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L,
3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L), levels = c("Tail", "Tail_b",
"Nose_b", "Nose"), class = "factor"), Millimetres = c(0, 0, 20.3,
74.9, 0, 0, 14, 63.7, 11.2, 2.8, 16.3, 72.6, 0, 0, 17.1, 72.5,
11.3, 2.9, 16.9, 74.7, 28.1, 4.9, 6.8, 37.7, 25.9, 5.2, 11.2,
68.1, 30.2, 6.35, 15.1, 76.2), Year = c("2010-2012", "2010-2012",
"2010-2012", "2010-2012", "2014", "2014", "2014", "2014", "2016",
"2016", "2016", "2016", "2023", "2023", "2023", "2023", "2024",
"2024", "2024", "2024", "2025C", "2025C", "2025C", "2025C", "2025B",
"2025B", "2025B", "2025B", "2026", "2026", "2026", "2026")), row.names = c("1",
"2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13",
"14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24",
"25", "26", "27", "28", "29", "30", "31", "32"), class = "data.frame")

Bob Green via R-help <r-help using r-project.org> escreveu (quinta,
8/10/2026 à(s) 11:19):
>
> Hello,
>
> I'm pretty rusty using R but wanted to compare
> four parameters measured in mm, in terms of the year an object was created.
>
> My problem is that where there are identical
> values, only one line is produced. For example,
> for the first parameter "tail",only five of a possible eight lines are visible.
>
> The code and full dataset are below. I considered
> making trivial differences to identical values of
> a parameter to create difference,but no doubt
> there are more elegant or sophisticated options.
>
> Any advice is appreciated,
>
> Bob
>
> library(ggplot2)
> library(tidyr)
> library(readxl)
> DF <- read_excel("C:/Files/DataLong.xlsx")
> DF
>
>
> DF$Parameter <- factor(DF$Parameter, levels =
> c("Tail", "Tail_b", "Noseb", "Nose"))
>
>
> ggplot(DF, aes(x = Parameter, y = Millimetres, color = Year, group = Year)) +
>    geom_line(linewidth = 1) +
>    geom_point(size = 2) + labs(title =
> "Parameters by Year", x = "Parameter", y = "Millimetres ($)") +
>    theme_minimal()
>
> ##Data
>
>
> # A tibble: 32 × 3
>     Parameter Millimetres Year
>     <fct>           <dbl> <chr>
>   1 Tail             0    2010-2012
>   2 Tail_b           0    2010-2012
>   3 Nose_b          20.3  2010-2012
>   4 Nose            74.9  2010-2012
>   5 Tail             0    2014
>   6 Tail_b           0    2014
>   7 Nose_b          14    2014
>   8 Nose            63.7  2014
>   9 Tail            11.2  2016
> 10 Tail_b           2.8  2016
> 11 Nose_b          16.3  2016
> 12 Nose            72.6  2016
> 13 Tail             0    2023
> 14 Tail_b           0    2023
> 15 Nose_b          17.1  2023
> 16 Nose            72.5  2023
> 17 Tail            11.3  2024
> 18 Tail_b           2.9  2024
> 19 Nose_b          16.9  2024
> 20 Nose            74.7  2024
> 21 Tail            28.1  2025C
> 22 Tail_b           4.9  2025C
> 23 Nose_b           6.8  2025C
> 24 Nose            37.7  2025C
> 25 Tail            25.9  2025B
> 26 Tail_b           5.2  2025B
> 27 Nose_b          11.2  2025B
> 28 Nose            68.1  2025B
> 29 Tail            30.2  2026
> 30 Tail_b           6.35 2026
> 31 Nose_b          15.1  2026
> 32 Nose            76.2  2026
>
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